Hello and welcome,
I've seen this model a lot, in several versions but often in mottled or an opaline style, coloured glass and also as lampshades. I'm pretty sure it's French from the 20ies, but I have never seen one that's marked in any way or even with a bronze mount, so I'm not sure if the mark refers to the glassmaker or the company who applied the bronze frame.
Do the initials say FBS?