In my search for items related to the U.S. 1871 military action in Korea, I came across this screw (1-1/4"L, 10tpi) in the area where we found .50-45 brass and shell fragments from a 12-pdr. howitzer. I have reason to believe one or more howitzers were later brought into that area. My question is if this screw might be related to the artillery (or something else the military might have been using) or is it just a modern piece of debris that got mixed into the area?