Bi-metallic coins and medals have been issued for a long time. The Roman Empire issued special-occasion, large medallions with a center of bronze or copper and an outer ring of orichalcum, starting with the reign of Hadrian. Meanwhile, circulating bi-metallic coins are known from the 17th century.[2][3]English farthings from 1684 through 1693 were made of tin with a central plug of copper for value. The silver-center centpattern produced by the United States in 1792 is another example.[2]
In the 1830s and 1840s, British medalist Joseph Moore produced large numbers of bi-metallic "penny model" and less common "halfpenny model" tokens, as a proposal to replace the relatively large penny and halfpenny coins.[4][5] Though not legal tender, Moore's tokens were circulated widely and accepted at face value by many merchants. Despite their popularity, the Royal Mint rejected the proposal, and did not reduce the size of the penny and halfpenny until decimalization.[6]
The first modern circulating bi-metallic coin was the Italian 500 lire, first issued in 1982.[7] Based on the minting process of the lire coin, the following issued bi-metallic coins for circulation were issued:[citation needed]
Costa Rica announced a bi-metallic 500-colones coin that will start to circulate in November 2021.[11]
The first ever tri-metallic circulating coins were 20-francs coins introduced in France and Monaco in 1992. These were similar to the corresponding bi-metallic 10-francs coins, but had two rings instead of one.
[edit]A Brazilian R$1 coin with its parts separated
The manufacturing process is similar to that of ordinary coins, except that two blanks (the inner and the outer) are struck at the same time, deforming the separate blanks sufficiently to hold them together.[13]
Countries
[edit]Countries with bimetallic coins in circulation. Gold denotes more than one bimetallic coin in use. Red denotes one bimetallic coin in use. Blue denotes that non-bimetallic coin of the same value circulates alongside the bimetallic coin.
^Leitão, P.J.; Teixeira, A.C.; Rodrigues, J.M.C.; Martins, P.A.F. (October 1997). "Development of an industrial process for minting a new type of bimetallic coin". Journal of Materials Processing Technology. 70 (1–3): 178–184. doi:10.1016/S0924-0136(97)02914-2.