finish mower

Hi All,
need help. Got a 3 blade finish mower I broke a blade on and the local mower shop won't order one unless I can give him a manufacturer. I have got no earthly idea who made this thing but I do have a few facts about the blade. The blade is 21 1/4" long, has 2 bolt holes on the diagonal of the blade 2 5/8" center to center, and a number of 50850 stamped in the blade....was told by the mower shop this was a pretty old finish mower due to the type of blade. Also the mower deck is pretty heavy built and is wrapped in treadplate type steel if this would help in identification
Regards... Rick Lahmann

I had an old Sunmaster deck that had spindles with the bolt holes drilled diagonally on the blade mounts. Had a hard time finding blades for it too.