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.