Technical Tuesday #1 – Machine Doubling vs. Doubled Die
There are two similar but distinct types of doubling that can appear on coinage, doubled dies and machine doubling. The distinction is subtle but can really impact a coins value, especially when a doubled die is the culprit.
This is the type of doubling that most collectors attribute mint errors to. Doubled dies occur during the actual die making process when multiple impressions from the working hub are needed for the die to be created. If there is any movement between the die or the hub, the doubling will occur on every coin made with that die.
Despite the fact that every coin produced with the doubled die will have the error, this type of doubling is very rare. The Mint is said to use 7-layers of redundant die inspections to eliminate the possibility of doubling. Regardless, there are still many well known examples, including the 1955 Lincoln cent. Doubled die coins can fetch a handsome premium on the market.
Also known as strike, ejection, and shift, this doubling occurs when the die strikes a planchet that is not correctly aligned. This can cause a slight movement or “bounce” at which point the machine strikes the planchet a second time. This error is very unlikely to duplicate itself so it does not create a variety, but rather more of a novelty type mint error. Machine doubling is commonly described to appear much more “flat” and does not produce the striking errors of doubled dies.
Machine doubled coins are much more common and therefor do not typically sell for the high premiums of doubled die errors.