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.
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
Examples
Two "Kelapa Sawit" (oil palm) bi-metallic Rp1,000 coins, with the second one being minted in 1996
^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.