I am by no means an expert on "relics" just enough to be dangerous. I have searched extensively for any information on your "dug in a farm field" besides the image posted here and the only other similar to identical is the one "dug" in Vicksburg. However, I have found an unending amount of pages in which there is a multitude of strikingly similar badges/insignia I found along with copious amounts of information on drummer, drum major, drum major military badges, pins and insignia and nearly everything available online points to
WW1 Musicians / Drum / Drummers / Bandsman Band Trade Arm / Sleeve Badge