Machine Doubling is when the press strikes the coin, and there is something that causes the dies to lift/jump just slightly and smear a portion of the devices out (the letters get thinner, since part is smeared out into the shelf looking area). Each is unique and can be in any direction. It seems to me to be an error - just not one the hobby pays much for because they are fairly common(except in an extreme case since a few people do collect them).
MD sort of looks like doubled dies (a variety) but you will learn to see the difference. A doubled die is when the making of the working die from the master is slightly offset between presses during its creation. This creates duplicates of the devices (they get wider/larger), but the duplicates are full height with the first device. This will happen to every coin struck with that die.
Edited by sheldius
01/03/2021 12:31 am