EMSCO 190 pumping unit 

They certainly do...

Base and gearbox had emsco on it. I believe national and emsco shared identical parts. Could be wrong...lol

@@matthewgreen8335, that would explain why both used that style of counterweights.

@@derekdz right. Kinda like Hesston and sentry. Different brand... same manufacturer and parts....

In my experience, all the (Continental) EMSCOs have that round crank arm, while nationals have straight arms with stack weights. I can't remember if pitman arms and wrist pins are same though, could be.