Bharpring's small buckle appears to be plain (unplated) brass. A kid's shoe-buckle (or watch-strap buckle, etc) from the 20th Century tended not to be plain brass, which would tarnish quickly, and leave a discoloration mark on clothing or wrist, etc. The form of Bharpring's buckle, although tiny, is the same as we see on 1700s shoe-buckles... having a "swell" (or "thickening") with a drilled hole at the middle of the top and bottom of the buckle's frame to accommodate a center-pin. (See the photo below.) So, in my opinion, Bharpring's find is a Colonial Era buckle of some kind.