I don't feel this is part of a trinket set, but what is it for? A square pressed glass box, 4½" square (115mm) and 2" deep (50mm). No real wear on either surface so I'm not even sure which way up it should be! The flat side is perhaps slightly more worn than the curved one but it's hard to see. Quite heavy for its size = 754g. No clues as to maker anywhere either. Thoughts welcome.