Hello,
If you are still trying to identify this piece, please post a few more photographs......especially the base rim, and some images of it laying down. Does it seem stable on its side? How much does it weigh?
Too big to be a stirrup cup, or a paperweight. They are even making glass shells for hermit crabs now, although it must be like going out naked, and I wouldn't want to meet the hermit crab that would be able to carry your piece! It does look like a shell sculpture from the first picture.
Michael Cohn and Molly Stone did some lovely shell paperweights, but I think they had solid bases. Not sure if they did any sculptures. Found one of their paperweights that appears to have a hollowed base - coincidently pink inside
http://vintageglasspaperweight.biz/2018/11/17/vintage-1993-signed-michael-cohn-molly-stone-art-studios-glass-shell-paperweight/Yours looks to be made of some quite nice crystal......does it have a ring to it? Do you think it is moulded or cut?
Waterford also did some nice crystal shells, but I haven't seen anything that wasn't clear crystal from them.
There are some lovely Murano shells, and there is something about the detail on yours that made me think of some of the Italian makers. But out of time for now.
Hopefully that's a start anyway.
Cat