Ok well my idea involves ancient money? Treasures ? From a non human entity, which have been threw extreme geological events over an extreme time span.
Martian trade tokens A couple saloon slabs. A Roswell hammered coin ride piece agenda token. Also a plutonic pewter megatron time traveler shift changing ID tag great finds.
My first thoughts they appear as if slightly melted but stone like. Makes me wonder if maybe the metaL used was extremely dirty and they were stripped of the metaL or it rusted away? I dunno just an idea