Showing posts with label Error Coins. Show all posts
Showing posts with label Error Coins. Show all posts

Error Coins - Mules - Part 6


This article gives out information on types of error coins. As the number of error coins classification is quite large, the article is divided into 6 Parts.
Part 1: Design Errors
Part 2: Die Making Errors
Part 3: Planchet Errors
Part 4: Strike Errors
Part 5: strike Errors Continued
Part 6: Mules
Part 7: Mis-Sold Mules

Mules:


[For other popular Mules that are actually Die-Varieties, refer to the next post]

These are errors where one side of the Obverse of a coin is struck with a Reverse Die of another coin or Vice Versa. These types of errors are rare compared to other types errors.

For a coin to be struck, it requires a pair of dies. Obverse and Reverse. In case of definitive’s, the Reverse is more often carried over from previous designs. In case of Commemoratives, the Obverse is more often carried over various designs. The Mint Master for any given coin decides the correct pair of Obverse and Reverse die’s to be used. In a mule error, the operator makes an error at the time of loading the die into the press.
In a strict definition, for a Mule error, the error must happen by the press operator at the time of loading the die. In other words, the the Mint Master knowingly determines that 2 dies are same and uses them interchangeably, then it would constitute a variety rather than Mule.
As what happens inside the mints is never known and hence it makes it very difficult for one to determine whether a particular coin a Die Variety or Mule. Quite a few times is very simple, take for example the Rs 5 with the Reverse of Rs 1 die or the Rs 2 coin with Reverse of Rs 10. By no stretch of imagination one can say that Mint Master intended to use these as the size itself is different. On the other hand there are certain coins in the recent times where the mints have been interchangeably using 2 to 3 types of Obverse dies. It then becomes difficult to predict and often is a matter of intense debates.

During discussing the mules quite a few numismatists use incorrect terms, for example they would say that there is a Mahavir Obverse or an ICDS Obverse etc. One should avoid such terms, and use it only for clarity . For example there is nothing called a Mahavir Obverse, the Obverse use in the Mahavir coin has been used for quite a few other coins before as well.
Criteria for Determining Mules:
In absence of what actually happens inside the mint, the guidelines for determining the mules would be;

  1. Do the Obverse [or Reverse] belong to different denomination that have a distinct design. If so its no arguments and one can easily call these Mules. The best example of these in Indian Coinage would be the Rs 2 definitive with Obverse of Rs 10 Definitive or Rs 5 with Rs 1.
  2. Are there pairing of 2 Obverse [or Reverse] dies, then its no brainer. The best example of these are Rs 5 of XIX Common Wealth Games and Rabindranath Tagore.
  3. Is there is distinct design adopted for the coin [mostly applicable for Commemoratives]. If so then anything else would be Mule. The best example of these are the 50 Paise of Indira Gandhi and the Rs 1 of Ambedkar. The coins had distinctive Obverse with dots around the periphery.
  4. Are the Coin boundaries sharp. If the coin boundaries are sharp, one can argue that a new die was introduced and the old discontinued. Hence any coin with the discontinued die would be a mule. These then fall into a debatable category. In certain cases it can be easily established, in other a study of all the coins in the period is required before one can conclude if it’s a Mule or not.
  5. Quantity Argument. Although not 100% right and true at all times, but the logic is eventually the mint operator would recognize a Mule error Sooner and recall the batch. Hence it is expected that on an overall basis, the quantity of Mules would be less compared to regular ones. However if it’s a Die Variety, one would have almost equal number of either coins. This again at times becomes speculative as it’s possible to be a Die Variation but struck with only one die and hence less in quantity. This would again need study of other coins in the period before one can conclude if it’s a Mule.
Myths:

  1. I have seen quite a few times the arguments; where both the coins are being manufactured parallel [or in same year], the reasoning that for mix-up to happen both the coins need to be minted at the same time. Although it makes the minting easier for mix-up, its is by no means mandatory.
  2. Coin boundaries are always sharp. IE when a new Die is introduced, the old one gets immediately discontinued. This is not true and there are quite a few times when the mint has used 2 dies in parallel for quite sometime. In such case all these become Die Varieties and not Mules.


1979 – 10 Paise – International Year of the Child
From 1974 to 1978, there were 5 commemorative coin in 10 paise denomination. All these used the Obverse die as shown in picture [extreme Right]. In the year 1979 for the 10 Paise of Happy Child Nation’s Pride, a new Obverse die type was created. This was slightly different from the older die in terms of font, lettering. and Ashoka Emblem [See Image on left].
There are certain coins, were the Obverse of the old type was used with this coin and hence a Mule.

For more details on various Obverse design, read the post here.



1985 - 50 Paise - Indira Gandhi Mule
A New Obverse design was introduced in 1985 to include “Satya Mave Jayate” as part of the Emblem. The RBI & Fisheries coin were to use this new Obverse. The Indira Gandhi coin also released in the same period had a different Obverse with predominant dots around to periphery to match the Reverse design. For more details on the various Obverse Die’s read the article here.



1985 - 50 Paise - Fisheries Mule
A New Obverse design was introduced in 1985 to include “Satya Mave Jayate” as part of the Emblem. The RBI & Fisheries coin were to use this new Obverse. The Indira Gandhi coin also released in the same period had a different Obverse with predominant dots around to periphery to match the Reverse design. For more details on the various Obverse Die’s on 50 paise denomination read the article here.






1991 B. R. Ambedkar
The Ambedkar coin has a matching Obverse with dots on the periphery. The Mule coin has the other type of Obverse that was used with ICDS and other older coins.




2006 – Rs 5 Jagath Guru Shree Narayana Gurudev – Mumbai Mint

The Narayana Gurudev had a distinct Obverse designed that had dots around the periphery. There are coins where the Obverse has a plain design. It can be argued that the dots design was only used on Gurudev coins and hence use of any other Obverse would be Mule. 


2008 Rs 2 Definitive with Reverse of Rs 10
The Bi-Metallic Rs 10 coins were minted from 2005, but introduced in circulation in 2008. The size of the Rs 10 coin is same as the Rs 2 coin, i.e. 27 mm. The Rs 2 Nritya Mudra coin had the Reverse as divided into 3 potions with India / Bharat at top in straight line. The Rs 10 coin had an Reverse design divided into 3 portions, however the date at bottom and Bharat / India at top where angular.


2008 Rs 5 Definitive with Reverse of 50 Paise
The Stainless Steel Definitive was minted in 2007 and 2008. A new Obverse was designed. The 50 paise coins were using the Nritya Mudra design. As the size of 50 Paise and Rs 5 coins are more or less same, i.e. 23 mm for Rs 5 coin and 22 mm for 50 paise coin. Notice the additional ring on the Mule coin due to the difference in the diameter.



2009 Rs 10 Definitive with Reverse of Rs 2
The Bi-Metallic Rs 10 coins were minted from 2005, but introduced in circulation in 2008. The size of the Rs 10 coin is same as the Rs 2 coin, i.e. 27 mm. The Rs 10 – 15 Rays [IT and Information Technology Design] coins were struck at the same time as Rs 2 definitive Nritya Mudra coin. The Rs 2 Reverse as divided into 3 potions with India / Bharat at top in straight line. The Rs 10 coin had an Reverse design divided into 3 portions, however the date at bottom and Bharat / India at top and bottom where angular.


Image and fine Credits: Abdulraziq Vhora


2010 – 5 Rupees – C Subramaniam – Mumbai Mint UNC Set
The strange story of this mule. The Obverse used here was the one from Rs 5 RBI coin. Amongst the coins in 2009 and 2010, only the RBI coin had a distinctive different design that was not used with any other commemoratives issued. Hence it is surprising to see the Obverse of Rs 5 that was used on the RBI. Further this is only in the UNC Set.
The UNC Sets were manufactured in 2 lots. Initially these were available from the Mint counter from January 2012 to April 2012. These coins had regular Obverse. The booking were invited in January 2012. Somewhere in May 2012 to July 2012, the UNC sets that were booked were being delivered, amongst them the first lot of deliveries had the coin with Obverse used for the RBI coin. Subsequent dispatches had the regular Obverse.
It is also difficult to treat this as Mule as it's in UNC Set. The UNC sets are supposed to be hand struck and each coin inspected [unlike mass produced coins for circulation]. Hence it can be argued that this was on purpose and hence can be treated as a Die Variety rather than a mule.


2010 Commonwealth Games from Kolkata mint
A Strange story of the Commonwealth games Mule. This would be the first coin without any denomination. This is because 2 Reverse were used. Instead of using an Obverse, a Reverse of Definitive was used.



2010 5 Rupees Rabindranath Tagore Kolkata mint
The Strange story continues with coins of Rabindranath Tagore from Kolkata Mint also not having any denominations. This is because 2 Reverse were used. Instead of using a Obverse, the Mint used a Reverse of definitive.

2011 – 5 Rupee – Definitive – Mumbai Mint
The Mumbai Mint has another interesting Mules after quite sometime. This time on the definitive of Rs 5 the Reverse of Rs 1 coin was used. Kolkata mint has outdone Mumbai Mint here by doing this for 3 consecutive years.


2011 – 5 Rupee – Definitive – Kolkata Mint
The Kolkata Mint continues with the trend of Mules, this time on the definitive of Rs 5 the Reverse of Rs 1 coin was used. Although quite a few Numismatist classify this as Mule, in true sense this is not a Mule but an error introduced at the time of creating working dies. Notice that the die size is 23 mm compared to the 22 mm of the Rs 1 coin. The 2012 coin is a mule in true sense, see the next picture.
The size of 23 mm means that at the time of making working dies, a 23 mm, Rs 5 die was hubbed with a Rs 1 [22 mm]. This is the most unique error in Indian Coinage, where the working die was wrongly created. This die was then used to strike Rs 5 coins.
Hence this would be classified as Die error rather then mule as the error was introduced more upstream and not by the operator at the time of loading the dies.





2012 – 2 Rupee – Definitive – Kolkata Mint
A very scarce Mule the Kolkata mint came up with in 2012. The Reverse was the Rs 5, a smaller die to strike the Rs 2 Coin.



Image Credits: Tanwer Alam


2012 – 5 Rupee – Definitive – Kolkata Mint
The Kolkata mint came up with a Mule in 2012, where they used the Reverse die of Rs 1 coin. As the size of Rs 1  die is 22 mm compared to 23 mm of Rs 5, notice the double ring formed. This coin can be called a mule than the earlier as the error here was on the part of the operator while loading the die.



2013 – 5 Rupee – Definitive – Kolkata Mint
The Kolkata mint repeated the 2012 with a similar Mule in 2013. Again they used the Reverse die of Rs 1 coin. As the size of Rs 1 die is 22 mm compared to 23 mm of Rs 5, notice the double ring formed.



2014 – 5 Rupee – Definitive – Mumbai Mint
The Mumbai Mint for the 2014, used the Rs 1 Reverse on the Rs 5 Coin. This is amongst the few errors done by the Mumbai Mint of definitive coinage.









Error Coins - Strike Errors - Part 5


This article gives out information on types of error coins. As the number of error coins classification is quite large, the article is divided into 6 Parts.

Part 1: Design Errors
Part 2: Die Making Errors
Part 3: Planchet Errors
Part 4: Strike Errors
Part 5: strike Errors Continued
Part 6: Mules

Struck on Wrong Planchet
This type of error occurs when the wrong size of planceht find their way in the striking chamber. For example a One Rupee Size planchet is put in the Two Rupee stamping press. This results in partial minting of the coin. There are multiple places where this can occur.
  • During the planchet making process, after the blanks are punched, some blanks are stuck / left over and get collected with the next lot of planchets.
  • During storage process, few stray planchets collected are tossed into wrong bins.
  • During the feeding process, the operator has put in a different lot of planchets. This typically happens when the sizes of the coins have got changed and operators make mistakes. However when such a error happens, the number of coins minted on wrong planchet are high [entire batch loaded] and get caught and the entire batch scrapped. However at times few may find there way into other batches and don’t get discarded.
  • In the stamping press few planchets from the previous run of different size remain. When the press is prepared for strike of different denomination coins, these find their way in striking chamber.




A new Rs 2 Coin on Rs 1 Flan


A Rs 2 RBI Commemorative on a Rs 1 Flang


A Rs 2 Cupro Nickel on a Rs 1 Cupro Nickel Flan. Its very difficult to notice this error as the coin size was almost same [Rs 1 is slightly smaller]. The only way to identify is look at the edges. The Rs 1 is circular and the Rs 2 is 12 sided.

Note: There are fakes of this type of error. Typically a normal coin is taken and cut into smaller size. The best way to identify this is by looking at the edge. It should be smooth and rounded. The size should be slightly larger than the planchet its stuck on as the metal would expand by the strike, the collars being too big for the small planchet.


Rotated Die:
Normally the Obverse and Reverse images of a coin remain upright. IE If one flips [rotate by 180 degree around the vertical axis] the coin the image is still upright. In a rotated die, the images are offset by various degrees. At times the rotation is as less at 15 degrees, at times 180 degrees. There are cases when the rotation is more than 180 and is nearly 350 degrees.

The Maharana Pratap Coin that was rotated by 15 Degrees.



The 1992 Coin that was rotated by 180 degrees


 



Indent:
In this type of error, a Blank [or previously stuck] Planchet [Coin] partially Overlaps another Planchet that is being struck in the striking chamber. The coin stuck will exhibit a blank area often at reduced thickness due to the pressure of the overlapping coin. The coin being stuck can be centred or off-centred.

There are always 2 coins involved in an Indent and both will show different errors.

Typically Indent errors occur with double strikes and depending on the sequence of strikes, different combinations are possible.

Simple Indent:
In the coin below, this was stuck only once; this coin was complete centred in the strike chamber. There was another coin below overlapping partially as well. The pressure / thickness difference caused the indent on this coin [notice the first image]. The other coin will also show an indent and a partial image on it. Notice the Obverse, the image is centred by only partial image is stuck. This is because of the difference in thickness, the coins do no lie flat, and hence the die is not able to put adequate pressure on this portion.







Off-centred strike to Indent with Double Strike
Here on the first strike, this coin was not completely in the strike chamber. This coin would on first strike cause an indent like the one above [Figure 1]. After this strike, the other coin would have got ejected. The image till this point in time on the coin would be only the indented one as seen in the second image. All other portion on both sides would be Blank. This coin has now moved into the strike chamber, centered. The second strike would now put all the other details.



Centred Strike with subsequent Indent:
Here the coin on first strike was stuck as a normal centred strike. However instead of getting ejected, it stayed in the strike chamber. Another coin got partial deposited in the strike chamber. The second strike created the indent on one side, as also overwrote partial details on the obverse.







Incorrect Die Pressure:
Normally when the coins are being stuck, the press holding the die comes down with a specified pressure on the Blanks creating the impression. Sometimes the die pressure is less due to malfunction or during shutting down of the press. Typically when the press is shut down, it may still hit few blanks before coming to stop.

This also happens when there is too much of Oil [used for lubrication and coolant] in the strike chamber. This reduces the pressure of the die on the planchet being stuck.






Blank Coin
As described in the die pressure error, this can happen during the time press is being stopped. Normally this is a known issue and the mint staff takes enough precautions to discard such coins.



Die Clash
This type of error occurs when the hammer die comes down on the Anvil die without a planchet to be stuck. The dies thus leave a weak impression of on each other. When the coins are minted with such pair of dies, they would show up the other images with weakness, also these would be mirror image of the actual images.






Withdrawl Doubling:
Apart from the doubling described that typically happen as Die errors, doubling errors can happen during strike as well. A common doubling of this type is when a worn die is used and it retracts faster than desired. The retraction pulls off some part of the metal that has not yet cooled, and the remaining part keeps flowing into the die.





Double Headed: Sholay Coin
This happens when instead of using an Obverse and Reverse pair of dies, the operator at the mint by error mounts both the Obverse or Reverse pair of die. Such types of errors are very unlikely today as the mounts of the Obverse and Reverse dies are different and reduce operator errors. This type of error is possible in older coin. There is no known coin of this type of error in Indian coinage. There are quite a few such fake coins minted to dupe collectors or used in magic tricks.










   
 

Error Coins - Strike Errors - Part 4


This article gives out information on types of error coins. As the number of error coins classification is quite large, the article is divided into 6 Parts.

Part 1: Design Errors
Part 2: Die Making Errors
Part 3: Planchet Errors
Part 4: Strike Errors
Part 5: strike Errors Continued
Part 6: Mules


Strike Errors
The strike errors occur during the manufacturing of the coins in the mint. There are different ways the strike errors can occur. Depending on this, they are classified as below;

Extra Metal:
This error can happen during the planchet process if the surface is uneven. However it can also happen during strike. An extra piece of metal [or any other material] comes inbetween the planchet and the dies. In aluminium coins if the metal is a broken off piece it easily fuses with the coin being stuck. This is because the temperatures in the strike process are sufficient to melt and fuse aluminium[1].


Note: [1] This can also happen if there is a die break in center. However this type of die break is rare and next to impossible. Typical die breaks are around the corners. Even if there is a center die break, the error will manifest as plane surface in that area, rather than extra thickness of the metal.

Broad strike:
This is the most routine type of coin error. Essentially in this type, the image does not occupy the correct position it is supposed to and is displaced. This occurs when the collar holding the blank malfunctions, thus the coin is not struck in the correct position.

A centered broadstrike with the collar missing, on Aluminium coins this often results the planchet getting cracked as it cannot take the force exerted by the strike, the coins also expands. The result is more pronounced on Aluminium coins than on steel or nickel coins.


A Off-Centered broadstrike, resulting in coin getting slightly out of shape.


A huge offcentered broadstrike, resulting in only a small portion of the image being stuck. The pressure results in the coin become very thin at the portion its stuck due to expansion of the metal.






Mis-Aligned Die Strike:

This is similar to Broadstrike, except that only one side of the coin is Off Center and the other side is perfectly centered. This happens when the hammer die and the Anvil die are not aligned correctly. The mis alignment can be due to improper mounting or calibration. However this gets caught very soon. The other way this can occur is when the die is not fitteded tightly and after multiple strikes causes the mis-alignment.


Brockage [Lakhi]:

This type of error was common in early mints and with modern mints this is reduced. Essentially in this type of error, the same image is stuck on both sides. On one side of the coin has normal image and the other side has the mirror image. This happens when a minted coin is stuck in the die and has not fallen off. When a new coin is minted, one side gets the normal impression from the die. The other side gets the impression from the coin that was stuck in the die.

One can distinguish between Observe and Reverse Brockage. Obverse brockages occur when the previously struck coin was not ejected and gets stuck to the lower die, and reverse brockages when the previously struck coin remains stuck to the upper die







Partial Brokrage:
This is similar to the Brokrage, however in this the coin that got stuck was off-center strike. Hence when this stuck the new coin, the Brokrage is partial and the image imprint is offset as seen in the below image. One can also notice light image of date that is stuck from the portion of Die that is not covered by the Brokrage Coin.


One Side Printing[1]
This is similar to Brokrage, except that the coin that was stuck in the die is a Blank, or by error the feeding fingers have deposited 2 coins on top of each other in the striking chamber.



Note: [1] There are quite a few fake coins passed off as this type of error. A normal coin is taken and milled. Refer to Fake Coins of Republic India book.



Split Planchet, After Strike:
Due to incorrect metal composition, the planchet splits into 2 after the strike. Thus this would be similar to one side printing error, the difference being the thickness of the coin will be half the normal thickenss. The surface would also be rougher on the side which got split. There could be weak design details in some cases depending on where the coin split


Split Planchet, Hinged:
This is similar to the above error, however instead of split portions being separated, they are held together by small portion or hinged on to one side. These are also often reffered as "Clamshells"


Multiple Strikes:
This type of error occurs when the same coin is struck multiple times, mostly the second strike is off center. This occurs when the coin does not get ejected by the feeding fingers and remains in the striking chamber. Typically in this type of error it can get stuck twice. However there are instances when it has been stuck multiple times.

The second strike typically overwrites all the features of the first strike in the area it is stuck.

Double Strike:



Multiple Strike:







Cracked Die:
This type of error occurs when the die wear causes a crack in the die. This is the first step towards a Die Break. More often the crack is not noticed. The crack normally splits the die typically into 2 portions. A coin stuck with such a die will allow the extra metal flow into the crack, giving a raised portion or a curved line to match the shape of the crack. Left unchecked, the die would break off. See next section.



Die Break:
This type of error occurs when the die used is damaged due to repeated strikes and is not replaced. This is the next stage of Die Crack that is not noticed or replaced. This gives a partial image of the coin on the blank planchet. The remaining area is raised. This is also sometimes called as Cud’s. The other side is struck properly

Major Die Break: CUD
In this a major portion of the die has broken off and quite a bit of area is not stuck. See image below.



Minor Die Break / Die Chip:
In this a small portion of the die breaks off, typically at the edges. This edge looks raised.




Broken Collar Die Break / Collar CUD:
A break in the collar can result in a lump or extra metal along a struck coins edge.



Error Coins - Planchet Errors - Part 3


This article gives out information on types of error coins. As the number of error coins classification is quite large, the article is divided into 6 Parts.

Part 1: Design Errors
Part 2: Die Making Errors
Part 3: Planchet Errors
Part 4: Strike Errors
Part 5: strike Errors Continued
Part 6: Mules



Planchet Errors:
This section gives out the details of the errors that can occur during creation of Planchet.

Incomplete / Chipped Planchet:
In this type of error, the Blank Planchet used to mint the coin is not of correct shape. This happens when the Blank is being created out of the metal sheet. There are multiple ways in which this error can happen. These are classified as; 

  • Rim Clip: Very small curved or straight portion of the rim/edge missing. 
  • Incomplete Clip: Long incuse curves on Obv. & Rev. due to an incomplete blank punch overlapping a previous punch. Considered Rare. 
  • Straight Clip: Similar to a Rim Clip only with a larger portion of the edge (2-3%+) missing along a straight or slightly bowed out line. 
  • Corner Clip: Coin struck on planchet created by a blank punched from the corner of metal strip. Very rare as only four even possible per roll of metal. 
  • Curved Clip: Similar to a Rim Clip only with a larger portion of the edge (2-3%+) missing along a inward curved line. 
  • Ragged Clip: Jagged fairly straight portion of the planchet edge missing. Considered a Defective Planchet if not straight and runs deep into planchet. 
  • Elliptical Clip: Oval shaped coin due to a complete blank punch overlapping a previous punch. Normally 'Elliptical' & 'Crescent' Clips created together. 
  • Disk Clip: Similar to a Rim Clip only even smaller and along the rim's edge. Seen on the Edge as an tiny indent or dip along the coin's copper core. 
  • Assay Clip: Blank/Planchet with a portion missing as if cut out. Very Rare. 
  • Crescent Clip: Similar to a curved clip only with 50% of the coin by wt. missing in an inward curve. Normally the other smaller half of an 'Elliptical Clip'. 

Below are some of the error types I found in the Indian coinage.

Type 1: Curved edge. This happens when the sheet does not move ahead by sufficient distance. The next punch will overlap an already punched area. This causes edge to have a curve. See images below.

Type 2: Double Curved edge: This happens when the sheet does not move ahead by sufficient distance and at the same time also moves sidewards [Sideward movements are not desired]. This causes a double curve.

Type 3: Straight Edge. This happens when the metal sheet is not feed correctly into the Blanking Press. The other way this can happen is during the advance of the metal, it also erroneously moves sidewards. The coins are punched towards the edge. This results in one side of the Planchet being straight.

Type 4: 2 Double Straight Edges. This is similar to Type 2, except that the blank is being stuck in the corner.

Type 5: Ragged Edge. This is similar to Type 2 or Type 3, except that the metal sheet being used here does not have a straight edge, but a highly uneven jagged edge.









Note:
It is important to note that at times these errors in coins can be intentional outside the mint. i.e. Fake Error Coin. The way to identify if a coin was chipped during the Blanking process or after it has been stuck is to observe the relief in design, especially near the cut portion. A coin which was stuck with a chipped planchet will show weakness in strike near the cut area; this is because the metal instead of flowing into the die expands outwards. The edges themselves will be more rounded that straight if cut later. The 10 Paise aluminium coins above look like cut after the coins left the mint.



Uneven Planchet Surface:
Normally the sheet used to create blanks / planchets has even and smooth surface. However at times due to impurities on the surface the sheet at places may not be smooth. At times its also possible that during transportation or handling, there are abrasions on the surface on the sheet. A planchet created from this area will still have the imperfection, the resulting coin will still show the imperfection and the metal flow is not sufficient to cover this up.

A good way to identify if the abrasion is not cause after minting and during circulation is to see the image on the coin, if it was there before strike; it will still show a weak imprint on those area’s. If it was after minting the coin, then there will be no imprint in that area.

Below an Rs 1 coin stuck on an imperfect planchet.




Missing Center
This is a new type of error in the Rs 10 Bi-Metallic Design. In this type of coins, there are 2 metals used of different combination. These are then fused under pressure. Sometimes the coins do not fuse well. The center piece comes off from the outer ring during the minting process. Thus the coin would be without a center piece. There would be other type of error where only the center piece is available and the outer ring is missing. However if the center piece is stuck offcenter, then it’s a Planchet error. If the strike is centered, it indicates that both the pieces of the Planchet was correct during the strike and came off after the strike.



OMS [Off Metal Strike]

This type of error happens when the coin is minted on a metal that it is not intended for. There are 2 ways in which this can occur;

One is the metal alloy that is being used to strike the coins comes in different alloy mix percentage than specified. For example the Ferritic stainless steel [FSS] used for the current coins is a combination of Iron 82% and Chromium 18%. If the metal delivered to mint comes in say more Iron content, say 90%, then the coin will be more Iron and will have different characteristics than the FSS.

The second way this can occur is if there are 2 coins being minted with similar metal [not distinguishable easily to normal eye] and there is a mix up in the feeding the metal alloy sheet to the blanking machine. For example from 1964 to 1971 the 50 Paise was minted using Pure Nickel, the 10 paise from 1964 to 1967 was minted in Cupro Nickel and from 1968 to 1971 it was Nickel Brass. All the metals look same in raw form and develop distinctive toning after finishing. Hence if Cupro Nickel sheet was used to mint the 50 Paise it would have been OMS. Note that for the coins specified there was a slight difference in thickness of the coins [which means that the OMS coins would have been of different thickness as well].

There are very few known and accepted OMS error coins in Republic India coinage.


1984 25 Paise coin
Below is an image of 1984 25 Paise coin that has more Iron content and hence magnetic. The actual metal for the year should be cupronickel. As to how this is possible is not known as Indian Coinage adopted Stainless steel for coins only in the year 1988.


2003 Rs 2 coin
Another coin is the 2003 Rs 2 coin that was minted using steel rather than cupronickel. This is possible as during that period Rs 1 coins were minted using steel, the diameter as well as thickness of the Rs 1 coin is similar to the Rs 2 cupronickel.




2003, Calcutta Mint
Another OMS struck in Cupro-Nickel in stead of stainless steel in the year 2003, one rupee coin.


Note: The size and thickness of the Rs 2 Cupronickel and the Rs 1 Stainless steel coins was similar. The above error could also be “Stuck on wrong Planchet” type of error [see section below]. As explained in more detail in that section, this can also occur due to stray planchets finding their way to incorrect pair of dies. So rather than classifying these as OMS, I am more inclined to classify these as “Struck on wrong Planchet”.


Thin / Thick / Weight Error:
This type of error occurs when the metal used for creating blanks is of different thickness than specified or is not rolled correctly for even thickness.

This error is typically on the metal sheet that the mint has procured and has failed prper quality checks. The thickness error can be both ways; i.e. the metal is of more thickness or of less thickness. This type of error is relatively rare.

The more common thickness error is as a result of the sheet not being rolled correctly of uniform thickness. IE the sheets tapers off upwards or downwards from one end to another end or is uneven in thickness throughout. It is more possible that this type of sheet can pass the quality checks.

There are supposed to be quite a few coins of Rs 2 cupro-nickel minted in 1997 from Hyderabad mint that are almost double the desired thickness or almost half the thickness, ie instead of 6 g, the coins are aprox of 9 g and 3 g. However I have not seen or come across such coins.


Split Planchet, Before Strike:
The Planchet splits into half before being struck because of improper metal composition used. Thus the coin will be exactly half as thick as desired. The strike itself would be weak as the pressure exerted by die is less.


Sintered Planchets:
In the process of creating Planchets, Blanks are often cleaned [to remove any dirt] and bathed in a chemical [to give distinctive toning]. During this process at times, the operators forget to replace the chemicals used for a previous batch run. Thus we have a dirty solution used to previously clean coins of different metal composition. This leads to trace amounts of other metal getting stuck to the surface of the Planchets being cleaned.This causes discoloration in pockets or in the whole planchet. Coins stuck with this Planchets will show discoloration.