including the glass being quite thin.
The glass looks thin enough, it is under 2" at the opening... quite hard to imagine so small which makes the glass seem super thick. Ray how does the thickness of the glass compare with Monart in general?
As to shape, it falls between W and XB and considering the size, a tad smaller than the average miniature, it does fall within the realms of possibility. Main fuzz factor is that the foot is not dusted. Which 99% are. An aside, I saw a cased foot piece recently, that is almost as rare.
My vote is possibly Monart. I doubt you could prove it further unless you found who it was made for... probably as a salt.