I'm sure 'concavity' is a word! :shock: If it wasn't, we would need to invent it, to describe the basal .... er.... concavity! of paperweights! :lol: :roll:
This one's base is quite noticeably concave, and it has no outer rim but finishes with a very clear line, so only very slight signs of wear can be seen under magnification at the extreme edge. The glass is very clear and free from any scuffs or scrapes, too.
Intriguing, eh? :?