Nice one! I'm no expert on this version, but the S marked versions were adopted for the Canadian no. 32 TP during WWII, under contract to the Canadian government.
I actually encountered something that I had never seen before, so I thought if I hadn't seen one others might find this interesting as well. This is the backstory: In early 1943, the Lyman Alaskan scope was actually the front runner to be used on the M1903A4. Ordnance wanted to name the...