1 Centime pattern in tin, Gengembre process

The Gengembre process was an experimental coinage method proposed in the mid-1790s as the Directory government struggled to stabilize a monetary system wrecked by the assignat collapse. Jean-Baptiste Gengembre's technique involved striking on tin planchets under modified pressure conditions, and the Monnaie de Paris produced a small series of pattern pieces to test its viability. The process was never adopted for circulation.

Tin was a poor long-term choice — too soft, too prone to oxidation — and that practical rejection is precisely why surviving examples are so seldom encountered outside institutional collections.