Based on other items I've gotten my hands on to sell, my best guess is that this item is part of an aqueous column plunger, Spectrum Chromatography item number 124136. But I can't guarantee that because this exact item's picture doesn't show up on their website...and the specs they show are for a device of a different design. I'm also not positive that this is the aqueous solvent model, though I feel that's much more likely, given the lab it was disposed from.
The overall length of this plunger is 20.9cm and the actual diameter is 4.9cm. When compressed, the two o-rings press outward to slightly over 5.0cm.
The o-rings are in excellent, like-new condition. The lower "grid," "fine mesh," are NOT INCLUDED, but the "snap ring" IS included, as shown in the pictures. (I have another one for sale with the grid, mesh, and snap ring included.)