These have been in production for a very long time. They have been designed by Gate in 1932, produced in the thirties, in the seventies and in the nineties with the same numbering - being 395 (the model) and /11, /12, /13 and /14 for the size. The number may be preceded by 1 or 0 - but I was unable to extract the precise meaning of that from the rather longish discussion on Antikprat on "Tusen Fönster" vases.
Maybe Bill Geary can tell you from the colour of the label when this one was made - but I'm not sure it is relevant.
Congratulations on your acquisition - which must be the best 1930s design from a top designer, top factory and top quality. Full marks, Max!