1863 Springfield style Leather Rifle Sling. It was removed from a Springfield Trapdoor military rifle. I have seen this style of sling on early muskets as well.
Top-Grain Leather Gun Sling Rifle Strap for. 12GA Shell holder Shotgun Sling? :This sling is specially made for bullet models such as 12 Guage. Note that 20GA and 16GA are not available.