is this a coffeemaker globe, or ???

This was one of the unbroken glass things I found amongst the rest of the stuff inside that 'china cabinet' that I picked up from the curb a few weeks ago. I've been wondering what it really is ever since.

My first thought is half of a "siphon type" coffeemaker. I've never had one of those, and am not all that certain exactly what they are, but somehow that thought came to me as what I thought I was looking for when I went googling for glass coffeemakers...??

It is shown here with the iced tea bottle for general size reference, it is about 6-1/2" high with roughly 4" and 5" open ends, each has a pair of small notches cast into it rim opposite each other. There are no marks.