You're right about it being Strombergshyttan. The "B" means vase, and 916 is the design number. At the end of 1954 the numbering was up to 642 and 972 in 1959-60, so 916 was between those years. Sorry, I don't know the exact meaning of the other set of numbers, but I'm pretty sure the numbers refer to the design of the engraving and/or engraver.
David