Hi Lynne, I have just been trying to understand some marks like this myself and I think that I might have sorted yours out as well. I have just found an engraved vase (pictured on page 178, bottom left of DKs 20th Century Glass by Judith Miller) with the marks; Orrefors P 3613.56.69
Which I believe translates as; Sven Palmqvist pattern no. 3613, designed in 1956, made in 1969.
The pattern number on yours is 1933 according to Ivo's super little book (page 108, Orrefors Marks on Engraved Glass, about 1/3rd the way down the left coloumn!) as they used numbers 1213-1294 in that year. Now I get a little more hazy but It seems more than coincidence that the next number on your (33) and mine (56) is the same as the year of design. What do you think, have I stretched it too far??? At least you have less numbers than me!