Well, nobody mentioned Belgium (VSL) yet. There are very few pattern books for the factory, but having just bought a large box of stuff which is definitely VSL, this piece would not be very out of place in it.
Very typical the deep and polished star-cut base which extends so near to the edge of the foot that it creates a reasonable rim (and reduces scratching on fine wood surfaces). Somewhat 'rounded' or 'soft' ribs are also a typical VSL feature
Although it's hard to tell from the pictures, the outside 'lip' looks rather over thick! I have quite a lot of Imwald and this is pretty near to the right 'scallop' shape, but most of MY Imwald is quite exactly proportioned (and therefore a somewhat slimmer edge), this looks to be quite chunky?!
(Pamela, I'm sure you have even more of it, so I bow to your greater knowledge)
One of the most noticeable things about VSL designs is that the glass is rather unnecessarily thick. (Perhaps they were selling stuff by the kilo!) ;-) (Though actually it's a better guess that they were shipping on the waterways and cared more about resilience than about weight!)
German factories generally(!) preferred a somewhat slimmer press-moulds (and Holland generally the 'thinnest' of all!)
PS. I fully agree with Glen that without the thing in my hands this is just a very obtuse guessing game!