What is a doubled-die? From a technical standpoint, it is my long-held opinion that any doubling on a die that occurred during its production, use or rework is a doubled-die. From my perspective, the term is very generic and encompasses many causes of doubling. In scholarly works, the term is too vague to stand alone unless the observer is presumed to know the process involved in creating it.

While the majority of marketable doubled-dies are the result of hub doubling and it is assumed the buyers know this or don't care, and the simplified term doubled-die is quite appropriate since the focus of an ad is not scholarly,. However, from a scholarly position, you may notice that some of the most advanced students denote the process within the name, at least in its first use in an article. In fact neither Alan Herbert or Del Romines, two of the leading scholars in this area, even use the term doubled-die to describe hub doubling.

To illustrate, an article I wrote on a 1935 doubled-die cent identified it as a hub-doubled-die while an article including information on the Disney "Dopey" medal with a "double foot", created due to a broken and reset cutter on a reduction lathe, was referred to as a reduction lathe doubled-die. In an article on the U.S. Navy Desert Storm medals with multiple die images, I referred to them as an EDM (or spark erosion) doubled-dies. Doubling on central devices resulting from multiple impressions into a die, often times through mechanical means via puncheons or partial hubs, I consider to be doubled-dies.

Since the hobby has evolved some very specific terminology for some of the forms of die doubling such as repunched Mint marks (RPMs) and repunched dates (RPDs) we tend to accept and use those terms outside the generic doubled-die designation. However, from a technical standpoint these too are also forms of die doubling or doubled-dies. Intentional rework or unintentional die deterioration that causes doubling of die designs is also technically a doubled-die but, like the above, they are forms of doubling covered by their own specific terms such as "engraving doubling", "die deterioration doubling" and "abrasion doubling." Specialists need to be careful of stating that a form of doubling like abrasion doubling is not a doubled-die. Abrasion doubling is the result of a "doubled-die" but not one we normally refer to in those terms.

Ken Potter is the official attributor and lister of world doubled dies for the Combined Organizations of Numismatic Error Collectors of America and for the National Collector's Association of Die Doubling. He privately lists U.S. doubled dies and other collectable variety types on both U.S. and world coins in the Variety Coin Register.

For more information on either of the clubs, or on how to get a variety listed in the Variety Coin Register, send a self addressed stamped long envelope to Ken Potter, P.O. Box 760232, Lathrup Village, MI 48076-0232. He may be contacted via e-mail at: [email protected] An Educational Image Gallery may be accessed on his website at: http://www.uscents.com/potter/.