Struck through lubrificant

Struck through lubricant is the most common type of minting error and occurs when lubricant from the machinery used for coin production greases the planchet or dies during the minting process. This error is generally evanescent and can partially or completely erase the design depending on the amount of lubricant that takes over between the die and the planchet at the moment of minting.

It is important to note that this type of error is often confused with weak strike, but there are significant differences. Struck through lubricant typically occurs only on the obverse or the reverse and never involves the side, although in minor cases, some elements of the imprint may be evanescent or absent on both sides of the coin. In contrast, weak strike errors always involve both sides of the coin, with proportional and specular weakness on the obverse and reverse, including the side in the most extreme cases.

To distinguish between these two errors, it is essential to observe the affected sides of the coin carefully. Weak strike errors will consistently exhibit weakness on both sides, whereas struck through lubricant will usually be confined to only one side. As such, it is relatively straightforward to tell these two errors apart once the differences are understood.