The buckle appears to be a variant of the Regulation 1874 Pattern Officer's Plate.
Pages 542 through 547 of American Military Belt Plates by O'Donnell and Campbell, show similar styles and examples, though not the exact match for the one we see here. The Regulation 1874 Pattern was in use, with slight changes and variations, through the 20th Century World Wars.
I see nothing that points to or yells out "Fake" here. Granted, there are literally tons of fake military items flooding the market place. However, the design details, attachment devices (or broken evidence in this case), patina, source, and other factors here all seem to support a legitimate military buckle find. Furthermore, this style of buckle is neither very rare nor highly valuable (which leads to the question: "Why produce a fake copy?").
Some of the rarer state militia and original Confederate issue buckles and plates are indeed well into the four figure range, consequently providing an attractive venue for copiers and fraudulent fakers. A Post American Civil War belt plate that would barely break the three figures on a good day though, is far from a likely candidate for a fake copy.
CC Hunter
