Mule, Muling. An obverse die mated with a reverse not originally intended. Also called hybrid. Muling takes place usually where a number of similar items are made at the same place and time. Obviously the diameters of both dies must be the same, and both dies suitable for the same press. Coins, medals and tokens have all been muled, some by accident (where the wrong die was inadvertently used). More often, however, it is done by later intent. In some instances a stock die, say the obverse, is used and a custom reverse die is made to mate with this obverse. (Two dies with original intent to be used together are called mated dies).

The reasons for muling are several: (1) to create a new variety for collector demand, (2) a new variety for sale to public, (3) to lower cost by using a stock die instead of preparing a new die, and (4) by capricious action or accident.

In the history of most mints and medal makers, examples of mules and muling are legion. Private mints are more apt to do muling than national mints, where more constraints are in force on their activity. Muling was rampant in England in the 1790s for halfpenny tokens produced by private mints; likewise muling was prevalent in the United States in the mid 19th century particularly for Civil War tokens and storecards. The medals of engravers of this period, John Adams Bolen and Joseph H. Merriam in particular, were widely muled.

Numismatists usually need to examine a large number of specimens, or to have intimate knowledge of a series to recognize a mule. By studying the die varieties and die wear the astute cataloger can gain insight into the sequence of use of dies with different mates. Then it will be the cataloger’s duty to chart the relationships between the dies. The chart would identify pieces which are die-linked. In fact such a chart is called a or simply a

A small number of die-linked specimens would form a simple chart. When photographs are used to illustrate mated die specimens and mule specimens, it is not necessary to obtain new photos of the same design again and again. A may be used of an existing photo of that variety with another existing photo to indicate the mule example.

Reference:

NE42 {1992} Doty, p 222.