Hi Emmi -
According to Andy McConnell's book at least some of these (with the cut diamond pattern) were made at Kosta and imported by Wuidart (see p. 226). There is a design drawing in the Kosta archive dated 20th October 1940, pattern 7534/W, with "J. Wuidart & Co." written at the top. I would imagine other factories made them too.
robbo