You should check into early silver coins from foreign countries that have the backs of them turned smooth. they are called love tokens, they were designed to be engraved as a souvenir, and usually sell for their metal weight. Often silver foreign coins, have less collectors value here, than domestic ones. A good example is Australian Florins, many were brought back by G.I.'s after WWII, and end up in coin shops, or junk stores.
I own a late period longrifle with both sterling, and German silver inlays. So, mixed materials is not out of the question.
Hungry Horse