Whilst I have no problems with the original 1942 oil pump, it pays to have a look when you have something apart.
All I have done with the pump is to clean it, measure it and function test it. Both supply and return plungers are within tolerance, as are their bores, and the check valves are working.
I've oiled it and refitted it with a new gasket. These eventually show patent number 325226. I wonder when the patent was granted?