I am stumped by this signed numbered overshot on clear glass torpedo vase. It is heavy about 1Kg with a beautiful flat polished rim. The overshot colour is a subtle olive green. It is about 8 inches tall and beautiful quality and carries a mixed initials and numbers monogram etched and spaced neatly on the base which appears like this: 530A 4
I thought it might be Scandinavian -Kosta maybe? - but would be so grateful if anyone could shed any light on identifying it.