In all of my error books there is no such term "mechanical Doubling. Can someone please explain this to me?
It is also sometimes called strike doubling and sometimes ejection doubling - but no matter what you call it it happens because one of the dies moves slightly when the coin is struck or when the dies separate in the instant after the strike. This causes metal to be moved on the surface of the coin. There is no doubling on the die, only on the coin. On a genuine doubled die - the doubling is on the die itself. And because of that of course it is imparted to all coins struck by that particular die. With mechanical doubling, it may occur to only coin or it may occur to many if the dies is loose in the press.
