Posted 10/27/2015 01:54 am
That is an electrotype shell that was never trimmed to size or backfilled with tin or lead. Electrotyping was developed in the late 1830's and was used to make inexpensive duplicates of coins, medals, and works of art up through the early 20th century. Basically, a mold is made of the object you want to duplicate, it is given a conductive coating, and then placed in an acid based electroplating bath until the plating is thick enough to be removed. Coins and medals could be left as uniface pieces or soldered together to make a full piece.
