As Steve already suggest, it looks like a suspender clip. But without knowing the dimensions, it might be a sash buckle.
Your find 'buckle' reminds me of the US 1854 Liberty Head Dollar, although your piece more likely dates to the late 1880s.
"This was the first gold dollar minted in America by the authority of Congress, and only lasted for 6 years before it was replaced by the larger, thinner Indian Head Type.
This type was only minted from 1849 to 1854."