Help dating No. 5 Wards Master

This is a cross post from r/woodworking

I recently bought this wards master #5 hand plane. Despite its rough appearance it's japanning is in excellent condition, the tote is in tact, the mechanism all seem to function, and there is a ton of iron left on this plane. I was trying to find more information about this plane but can't seem to find much about it. It has a twisted lateral with a disc, it has wards master quality stamped into the iron at the top, made in USA on the front of the body and no #5 on the back. No patant numbers anywhere. Interestingly enough there is no rear frog adjustment screw.

Anybody have insights or resources where I can find out more about this plane?