PART VI. Striking Errors

Machine Doubling:

Isolated Machine Doubling

Definition: Isolated machine doubling affects only a small portion of an area without affecting the surrounding features.  This affect is most often encountered on the mintmark, since the mintmark is often fractionally higher than surrounding features and thus more vulnerable to impact the retreating die.

The image above shows a 2000-P Sacagawea dollar with isolated machine doubling affecting the P-mintmark.

The 1946-D Roosevelt dime shown above has its mintmark subjected to machine doubling. None of the surrounding design elements show this  doubling affect. Notice that the mintmark has two shelf like steps indicating that this may have been caused by a chattering die.