I saw it first hand and don't ever remember seeing another one like it. I figured out where that old house site is too.....on the south side of that farm road almost opposite the old red barn......I think we walked right by it and just didn't check that one area. We need to go back again sometime.
That buckle is called a Union Loop "loose roller" buckle off of a harness. The original patent was held by David White and carries a patent date of 1901.
That's not to say that they didn't exist prior to this time, and the name alone makes one curious about their origins.
All I can do to date it, however, is to go by the patent date.