Hello Mr. Turnip, welcome to the gmb!

I think you're spot on with relatively modern, but a bit further east than Poland. Contemporary Polish glass normally has a properly polished base, while contemporary Chinese glass tends to have this roughly ground finish.
I would also have expected the bubbles in the base to be regular and controlled and the same size if it was Polish.
However, I believe there are now a fair number of Polish masterglassmakers who are working in China, teaching makers there how to produce far better quality work.