unusual 'hollow' glass bowl

Found myself this odd clear glass bowl at Goodwill yesterday. As soon as I picked it up I kinda liked it. :-) It is about 7-1/2" across and 4" high, made of rather thick glass, and features an unusual 'hollow' design, with a roughly 2-1/2" round opening (w/ground edge) as its base. I've used a few handy glass marbles in pics 3 and 4 to try to display the way it is made, with a smaller (maybe 2-3/4" deep) 'inner bowl' basically suspended within its larger 'outer bowl'. Other than a couple tiny fleabites around the inner (thin) edge of its base opening, there are no marks whatsoever on it.

Does anybody recognize anything about it to suggest who made it or where it might have come from? I wouldn't guess it is anything terribly "old" or "special" (considering the source, after all) in any way, but OTOH, I'm not sure I've ever seen anything else like it either -- and it *does* appear to be rather nicely made...?? Frankly, my initial thought was to use it to display a small handful of pretty colored 'stone eggs' I otherwise have laying around here because it seems like it should be heavy enough to do so reasonably safely...but if it *is* actually a "something", mebbe I shouldn't pile it full of rocks...??

Thoughts/comments from all y'all who actually *do* know stuff about pretty glass things are MORE THAN WELCOMED to share your guesses, please?!! :-) :-) :-)