Possibly made by same country gunsmith as my great-grandpa's half stock, hanging over the fireplace, also 36" x 1" x 12# x .35 caliber. He lived in NW Morgan Co., served 90 days in Benton Co. Home Guards, then 3 years in Co. K, 25th Illinois Infantry which he joined 30 Sept 1861 when they were encamped at Otterville.

Does your ancestor's gun also have double set triggers?