Part V. Planchet Errors:

Rolling Mill Errors:

Rolling Indentation

Definition: A foreign object is rolled into the coin metal strip and falls out after the strip is rolled to final thickness.
The object can remain embedded in the subsequent blank or planchet but falls out before the planchet arrives at the coinage press.  The result is an underweight blank that has a recess on one face.  When struck, the coin displays that same recess and also shows weakness in the same area on the opposite face.

This 1980 cent shows a bowtie-shaped rolling indentation on the reverse face.  The indentation is too elongate to represent the impression of a bowtie clip planchet or a piece of chopped webbing.  The obverse face shows weakness opposite the recess.  The coin weighs 2.79 grams, significantly less than the 3.1 grams of a normal copper-alloy cent.

For more information on this error type see the February 7, 2011 Coin World.