What kind of bottle is this?

Dug a lot of old bottles out of a dump site on our property and found this.

I wonder, wonder if this might be a glass version of what is now plastic...found floating in the water tank of toilets everywhere??

I think it must be a toilet float . . . It seems obvious, now that Chris has pointed it out.

That was my first thought also but glass? Have you ever seen another one before?

I forgot to mention it also has a rubber stopper inside that I can't get out.