The correct name for this item is "Rope, Drag, with Shoulder-Strap, M-1918." It was used for pulling artillery pieces, etc and was not a mountain troop item. The 1918 in the name makes it clear that these straps predate the creation of the mountain troops by twenty-four year.

This type of strap has appeared on the internet multiple times under a variety of names and is often described as mountain troop equipment, usually in some way related to pulling sleds. In this case the seller described it as " a pair of 42 dated toggle straps used by mountain troops and engineers to lug or carry gear".