Google is your friend:
https://en.m.wikipedia.org/wiki/White_metal
White metal can be just about anything. Just like pot metal (another “glob” of many types of metals that melt around the temp of Pb/Sz/Sn.
Hallmarks & touchmarks on the bottom are your leeeeetle friend! Pass on all those cute little picture frames, ornaments, doo-dads, figurines, etc you may think are cheap sources of pewter!