My guess is it probably fit down over a spindle of some sort. As a decorative cover. My mom was an antique dealer and I grew up in antique shops. But there are so many things that are antique or collectible that I have never seen. I haven't ever seen one of these. My first thought was maybe it came off of something and worked as a handle. but as it is glass that isn't likely.
I asked my mom and she hasn't seen anything like it either. I use to have a book on glass jars and vials. You might look online for something like that.
Another thought I collect perfume jars and it could be an old vial for perfume or spices or something like that. It reminds me of a science lab tube. Since it doesn't stand it probably sat in a stand of some sort.