That's interesting - I've never heard of anybody being able to get in contact with Krosno!
The only thing I've managed to glean is that it is not a manufacturer as such, just an area of Poland where a lot of glass is made,and subsequently sold under the ageis of the Krosno name.
Labelled pieces are fairly thin on the ground, and do not tend, as far as I know, to be recent. I have a vase I brought back from Holland and a very nice pair of candlesticks. I had a fabulous decanter but I gave it away to somebody who lusted after it, and they went on to smash it. A retail organisation called LSA seemed to have taken over whant Krosno used to do, but on a much bigger scale and including all sorts of homewares and ceramics. Mostly, you see LSA lables on the sorts of things you used to see Krosno labels on.
If anybody knows more than that, or if I'm all wrong, I'd love to be put right or hear about it.