That hole does look like for coolant drain if it goes all the way through to the recess in the table. And if it does then that's probably what those rubber pieces are for, plugs to help stop coolant from flowing out the sides of the table.I probably should have qualified - mine is a '935' mill, not PM-935. Suspect the same machine but since I thought I saw same rubber on PM machines figured I'd ask here. Anyway this shows the rubber & how it stands proud of mill table which I find odd. I'd rather have it flush or recessed so table protection mats don't rise up on the ends or any chance of misaligned extended stock. My table also has a threaded coolant hole in both L&R pocket so the damn/diversion makes sense. I don't use flood right now so they are basically open.
The Millrite has cast iron end caps, which also serve to hold the lead screw bearings. There is no gasket from the factory(!) A little gasket eliminator does the job of containing the coolant, the machined fit is tight between the end cap and the table. The overall stickout of the lead screw is probably about the same with both types.The Millrite end cap above is nice, but a much bigger piece with a lot more machining, and I'm guessing it has a hidden gasket to seal the deal between it and the table.