Engrailed, Engrailment. A ring of dots or other ornaments indented into the edge of a coin or medal. The word comes from heraldry where engrail means an edge of small indented curves. In coining, engrailment is applied to the edge of the blank before the piece is struck. Like any edge treatment, its purpose is to discourage counterfeiting, prevent scraping surface metal from the edge and add decoration.

History of engrailed edges. A Frenchman, Jean Castaing, invented the machine that added ornaments to the edge of a coin in the 16th century. In Paris in 1555, Aubin Olivier attempted to accomplish this, not in the castaing machine, but in a collar while the coin was struck in a screw press. Later the canneluring machine was developed, an improvement of Castaing's method of treating the coin blank before it is struck.

How engrailed edges are formed. Engrailment is accomplished by rolling the blank between two metal bars, both grooved, but one having the design of dots or ornaments engraved in the groove. This takes place in either the canneluring or castaing machine. This action accomplishes, somewhat, the same function as upsetting (which wasn't in widespread use until the early 19th century) but upsetting thickens the edge without adding any edge design.

The blank with the engrailed edge is then fed into the coining press. Since the engrailment is sunken into he edge it is not damaged when the piece is struck within the collar in the press (although the edge may be slightly compressed by this action). See edge lettering and numbering.