Struck through fragment

The struck through fragment is a type of coin error that occurs when a metal fragment becomes trapped in the beating chamber along with the newly inserted planchet and is subsequently struck by dies at the same time. The fragment then detaches from the newly minted coin, leaving behind a cavity with variable width and depth according to its size.

When the planchet is beaten through a fairly thin fragment, the ridges of the coin may be partially visible inside the cavity. This mistake is often mistakenly referred to as a metal deficiency. However, it is important to distinguish between the two errors by examining the weight of the coin. If the weight is correct, it is a coin struck through a metal fragment; otherwise, it is a lamination error.