Quote:From seattleMD
seattleMD
Valued Member
Regarding your questions of
Machine Doubling vs Die Doubling:
Machine Doubling results in normally flat and shelf-like doubling. It is usually much shallower than the device being doubled. I believe it is normally a result of nuances in how the coin is struck and how the dies shift when they impact and lift off the coin.
Die Doubling is normally rounded and results in separation lines and corner notches on smaller devices. Die Doubling effects on larger devices is harder to distinguish (at least for me).
Die Deterioration Doubling, which is the third type of doubling commonly mistaken for Die Doubling, sometimes appears similar to
Machine Doubling, but in general occurs in the direction the metal flows - away from the center of the coin. If you see a device that appears thinner than normal and the doubling occurs on both sides, this is what I normally attribute to
Die Deterioration Doubling.
These are general guidelines that I follow. There are always exceptions to the case though and the more experienced folks on here can help when you're not sure. Sometimes simply a photo will not be enough and you'll need to send it in for closer examination by hand from a professional attributer.