endangered specie

Via TYWKIDBI (and indeed, we’d have no inkling otherwise), we learn that during copper and other metal shortages during World War II, the US mint experimented with various substitute materials, including pennies made of glass.
A possibly unique prototype sold at auction to one anonymous numismatist for a considerable sum—the batch made of this particular specie rejected and destroyed since it was a difficult medium to work with and there was no consistency in the quality. The following year, the mint issued steel pennies electroplated with zinc, and I’m pretty sure we have at least one of those around somewhere.