I could not find any marks anywhere but I would say by the look and feel of this it is likely WW1 era. The smaller strap side is 24.5 inches lone with the total length (including fold) of the larger side at about 50 inches. Very thick and heavy leather intended for military use. The item “M1907 LEATHER RIFLE SLING SPRINGFIELD M1 GARAND M1903 WWI WWII” is in sale since Monday, April 30, 2018. This item is in the category “Collectibles\Militaria\WW I (1914-18)\Original Period Items\United States\Personal, Field Gear”. The seller is “laz-e-bid” and is located in Alexandria, Kentucky. This item can be shipped worldwide.
I bent each pair of frog holes and no cracks. Normal creases here and there. Brass hardware with slight green around some edges. The color is a nice medium brown with some changes in color depth. The leather is soft and pliable. The stitching is very strong. This is a very nice sling. The item “M1907 LEATHER RIFLE SLING M1 GARAND SPRINGFIELD 03 ORIGINAL NO CRACKS BRASS” is in sale since Thursday, January 25, 2018. This item is in the category “Collectibles\Militaria\WW II (1939-45)\Original Period Items\United States\Field Gear, Equipment”. The seller is “scoutbovat2013″ and is located in Glenmont, New York. This item can be shipped worldwide.