following on from this and the linked post I checked in the swedish glass factories book. In Kosta 1959 (p 397 my copy) there are a number of bits by Ellis Berg - "the letters BH refer to designs by Ellis Bergh, in various techniques, which were either still being produced in the later 1950s or had been reintroduced. The item numbers facilitate dating of the designs." There's then a table with dates of designs.
This piece is in there with the number BH 1900 - which dates it as 1940 for the design. The fact that yours is B1900 and not BH 1900 points to one of the earlier made bits (in one of the earlier pages in the book are some designs labelled B xxx, which appear to be by Bergh also).
Gareth