Found this stirrup early in 2014 at an old homestead. Just completed electrolysis and wax. Details: approx measurements are 124mm x 126mm x 38mm. Any info on origin, type, or approx time of manufacturing is appreciated.
I know nothing about millimeters. Your find is a typical iron stirrup, off of military or civilian English style riding saddles. Also it's possible that it's off a side saddle. That said, you might be interested in this link. Diagnostic Artifacts in Maryland