Hi Elaine, you've managed to upload the bigger images beautifully, well done. The mark used on your glass was registered as a trademark by Krosno Glass S.A. around 2003 which gives you the earliest date this piece could be.
There are a number of glassworks in the town of Krosno, for example
Józefina (started 1980), Makora (started 1991), and
Glass Studio Habrat (started 1997) are others you might see, along with the maker of your piece
Krosno Glass S.A. (started 1923).
I can't find your item in the few Krosno catalogues I have copies of, but I've no doubt it's a genuine piece of Krosno.