Military sling for the Winder musket|What's New!|Forum|Winchester Collector

Folks, I recently purchased Winder musket 111683 from the grandson of the original owner. James Blackhall served in the National Guard in PA and OH before being sent to France in 1917 as an officer. He was discharged in 1919. He was a keen shooter and competed in Army matches using his Krag-Jorgenson and this Winder musket which he and his descendants have preserved in excellent condition. It came to me with its military sling in very good condition, despite having suffered a break at a weak point (see photos). The receiver was serialized in 1911 but the sling is dated 1918. In one stamping, the markings seem to say HOYT above 1918 and then a third line which I cannot read. In another position there are what seem to be three letters, perhaps GCK, above the 1918. It is possible that the musket sat in the arsenal for several years before being sold off as surplus, perhaps in 1919 or later, in which case perhaps a new sling was provided on disposal. Possibly Blackhall was able to select it for himself for use in matches and later bought it from the Army or had access to a supply of Army slings and had a new one put on the gun (I can only speculate). As regards the sling, I wonder whether anyone has knowledge of the markings applied to Winder slings and can explain them. The leather is in good shape (not fragile) but it could use feeding and the brass could use cleaning. Can anyone with experience of 100 year old sling leather offer some suggestions about treatments which will help it survive better and not damage it further? I have been told that feeding old leather can make things worse.