got permission to hunt a well hunted site last weekend. picked up a couple of goodies including the silver 1923 merc. the flat button has london written on the back not sure of date, no design on the front.
It is actually the drag to a sword scabbard with brass end-cap. My gut would say probably an NCO sword or musicians sword. it could also be from a post-war fraternal sword - though being where you would it I would say it certainly could be CW era.
thanks so much for the input, my hope is to go back one day if the owner lets me. the funny thing is i didnt know a big battle went on there untill i saw the monument, which freaked me out. i wanted to hunt it because of the late 1800 home he was living in. his yard has never been hunted he said and wont let you but he let me hunt close
Nhbenz is correct, and so is HomeGuardDan's more-specific answer. It is the brass "end-cap" known as the sword-scabbard's "drag." Even more specifically, it is part of the drag from a US Model-1840 NCO (No-Commisioned-Officer) and Musician sword's scabbard. (I should mention, that model was still being manufactured during the civil war.) Although it's true that many Fraternal swords and their scabbards more-or-less copied the US Army Model-1840 sword's form, your brass scabbard-drag is an EXACT match for the US Military model-1840s drag. Note the shape of the flat "side-ridges," the width of each of the flat ridges, and especially the location of the little valleys in the ridges. Unfortunately I don't have a close-up photo of a Model-1840s scabbard-drag, but perhaps you can see its exact form by enlarging this photo.
I've seen the narrow brass "double-loop" used as an adjuster on civil war era swordbelts. Sorry, I don't know which specific model of swordbelt. (I must mention, it may have also been used on other types of belts.) Perhaps it was on the belt your scabbard-drag was used with.