Curiouser and curiouser..
Swedish Glass Factories shows your decanter, (long neck, lozenge-like stopper, fairly stubby body) in clear
glass with the mark LU154/8 on page 85. The catalogue is from April 1934
It doesn't appear again as far as I can see
either in clear or frosted in the LU 154 series. Perhaps someone with sharper eyes can help..