I'm not sure it's conclusively
Krosno. It's very
like their glass, but there's a LOT of companies that made/make similar glass. I bought a vase in Woolworths for about £3.99 that had an identical bubble in the base. :?
Sorry to be vague...but when a design becomes popular, everyone jumps on the bandwagon and makes something similar - it can be a bit of a minefield. As Della says, Krosno is a good place to start looking.