Hi Bryn,
This exact shape is not in my book, but then again, it only addresses a fraction of Horbowy's wonderful designs.
Oddly, when it comes to (designer) Polish glass, there is no standard base finish. I have seen Horbowy pieces with a highly polished and flat base; with a neat, polished, concave center; with a smoothed pontil mark; and with a rough pontil mark.
I am 95% certain your vase is Polish. The GMB is filled with very knowledgable collectors -- If no one is able to come along to say it's from another country and designer, then I'll be 99% satisfied that it is a Horbowy design.
Anik
