button identification

Hello fellow enthusiasts! Yesterday I dug up a button around an old 1850s farmhouse in southern New Hampshire. I’d like help gathering more information about it. It seems to be gold plated on one side. I can read “IMPERIAL GILT”. 20mm in diameter and read up as 78 on my Garrett ace 300. Thanks...

After hours of research, I am still unable to identify this symbol/insignia. If you know anything about this button, please share your knowledge. I've taken photos of the fronts and backs of the buttons I own. Some are one piece plus the shank; others are two pieces. Hope you're not as baffled...