Thanks for offering to help. The question, for me at least, is what are the markings on the unique examples? I assumed that if the numbers were preceded by "Nr" it would be unique, that is pre-1960. However, my Kraka is marked exactly the same as the example posted on p. 169 of 'Glas in Schweden," also an, "Nr 322." See my photograph on previous post. Just looked at my other Kraka, which marked "Nr 52 C," which makes it, as I figure it out, from 1946-8. As it has no bubbles, it must be pre-1947.