Mule or Die Variation or Error - The Debate

I see quite a few items on eBay for sale [or with dealers] with the title Mule or Die Variations. Although the 2 are distinct, in many cases they are mis-sold to make fast buck. In essence Die Variations are more common and Mules are relatively rare.

This article tries to explain the difference between them. The key difference between the Mule and Die Variation is as to where the error occurred.

Before we proceed further, let’s understand as to how this looks. Typically one would notice small variations in the coin design on one of the face. The difference can be thicker features or smaller lion or lettering or any such features. At times these are very easy is distinguish, at times the difference is in millimeters making it difficult to recognize for an untrained eye.

If the error occurred at the time of creating working dies / hub from Master Dies/ Mother Hub, then it’s a Die Variation.

If the error occurred during loading of the die into the press, i.e. a die meant for minting one type of coin is put into the press meant for other. For example the Obverse of 50 Paise of Indira Gandhi being put in the press to mint the Fisheries coin and Vice versa. Typically for this type of error to occur, both the coins should be of the same size. In Indian coins, the Rs 5 and the older 50 paise were of the similar size; Or more recently the Rs 1 and Rs 5. The error can also occur if multiple commemoratives of same denominations are being minted. The 50 Paise Fisheries and Indira Gandhi are good examples of this.


Typical Die Variations
This section gives out the typical Die Variations one encounters.
Lion Varieties:
In Indian coinage, there are 2 distinct lions used, one Master Die created by Kolkata Mint that has more furry Lion and the other by Mumbai Mint. Generally the Mumbai Mint Lion is Thinner [or smaller] compared to Kolkata Mint. The best example of usage of different Lions is the Rs 2 definitive series were quite a few Lion varieties have been used and are found in plenty.

Date Difference
The dates are hand punched on the working dies as the last step in die creation. Variations can occur depending on how the dates were punched, slanting “9” or distance between numbers may vary. There are quite a few variations as the punch used are different.

Mint marks
The mint marks are punched on the working dies as the last step in die creation. The variation in this would be thick mark vs thin mark.

The dispute
Although the definition is quite simple and agreed upon, what is a Mule[treated as error] and what is a die variation is hotly contested topic amongst coin experts. There are similar disputes with other errors.

Mule Vs Die Variation Dispute:

This essentially boils down to proving “the intent” that the error was because of operator or because it was on purpose

Take for example the recent Rs 5 issues from 2005 to 2007 came in both cupro-nickel as well as stainless steel metals. Typically the cupro-nickel show deep features on the coins where as the stainless steel coins show weak featurs. However there are some stainless steel coins that show deap features, now comes the tricky part; to establish the intent.

The notable ones being called Mule or Die Variety being the 75 Years of Dandi March, Mahatma Basaweshwar, Jagath Guru Sree Narayana Gurudev, State Bank of India and so on

1. The Mule theory experts say that there were 2 distinct dies created, and the cupro-nickel die was used by mistake on the stainless steel coins.
2. The Die Variation experts argue that yes there were distinct dies created, because one needed better features on the proof & UNC sets. It does not mean that mint masters had no intention of used these on stainless steel. The fact that they have consistently used on most of the steel coins of different themes indicate that by design they were meant to be used. Not by error and hence these become die variations and not Mules.
3. The Mule theory experts point out that there are few commemorative coins where this is not seen.
4. The Die Variation experts argue that it would have been on all steel coins as needed. The fact that one has not seen it few themes does not mean that such varieties do not exist, plus usage of Cupro Nickel die on quite a few occasion points to the fact that this was not due to error, but was as required.
5. The Mintage would have been a clincher, it if its by error [mule], then the mintage should be as long as a pair of die last or the error is noticed by operator sooner or later. If it was by design the quantity would be quite large. However the amount of coins being minted in excess of 1,000,000 its difficult to lay down a precise number to such coins.

The same debate essentially carries over to quite a few other coins, like the Rs 5 cupro-nickel. Here there are 2 different Obverse used, one predominantly used with the coins minted in 2009 and the other for use with the coins minted in 2010. With the exception of the Obverse of RBI that has a totally different design and has not been used on any other coins;

1. The argument is that some coins have Obverse that is different. 
2. The variants experts point out that 2 master dies were created and the intention was always to used then as and when it’s required. It’s a routine policy of the mints to use older dies in case current dies wear out / break more than anticipated.

The dealers take advantage of such difference in view points and start selling the items at much greater price than it should command. Normally a Die Variation commands a very small premium and a Mule much higher premium. Hence calling something a Mule is more lucrative for the dealers.

Die Crack & Coin Edges:

The other definition for error and die variation is that for error, it has to be unique and not reproducible. It is reproducible then it’s a Die Variation and not an error. So for more errors say Broad Strike, Brockrage, its agreed by both the parties that these are errors as not 2 coins will have the exact same broad strike.

However matters become more complicated with die cracks. It argued that it has to be treated as variation as the exact same error occurs in tons on coins minted using that pair. Similar argument is extended to coins having plain edges instead of milled edges or milled edges instead of security edges.

The Error experts hold the view point that any coin that is not minted as desired, due to human or process failure is an error, irrespective on how the error repeats. Hence by this definition, all the die crack or different edge coins are errors.

The edge errors posses more challenge, as the number coins minted with incorrect edges is typically large and treating this as error becomes more difficult, further most of the issues have such edge issues. Hence calling it a variety is simpler.


This debate has been for ages and shows no signs of abating. Once you get more fascinated about the entire process, you can make your opinion and join the respective bandwagon. There is no right or wrong, one just need to convince that his point of view is right.