yes, it does appear to be Sowerby - pattern/design No. 2592, available in flint/amber/blue and green in the size of 8" only it seems.
I suspect a not uncommon piece, and made during the 1940's and 1950's
Thanks as always to Pamela for all information showing on the 'pressglas-pavillon', and obviously to the Thistlewoods for their CD compilation of the Sowbery factory information. The CD's are very worth obtaining if you have an interest in C20 pressed glass.
As to treatment of the misty/cloudiness inside the vase - we've spilled oceans of ink in the past on this subject - try a cominbation of word entries on the Board's search facility and you'r bound to find something of interest.
You might just briefly try some Cif on a cloth, plus elbow grease, and see if that achieves any improvement - failing which give the vase away and wait until you finde a clean one.