I can't be much positive help as this code doesn't seem to conform to the code used in the 50's and 60's, which would have two letters in front of the numbers, the first for the artist, the second for the production method (hand formed glass, cut glass, etc). The four numbers would be a production code. The code doesn't conform either to the post 1970's code.
My guess is that it's a Lindstrand piece, production number 1826, which would have been produced after the period "Swedish Glass Factories" covers. Why the "O" I have no idea. O was code for Ollers, but this isn't one of his pieces.
I'll be interested to see what comes up here.