I can't figure out what this piece is. On the bottom there is a nob that will tighten if you turn it all the way right, and a spring loaded plunger, as if to activate something when you set it down and the plunger is pushed in. If you unscrew the top a bit, you see that the glass has a neck on it and a cork in the top. The glass looks to be sealed on the bottom, just like a bottle more or less. Any ideas?