From the article posted....
snip
However a unique serial number that Winchester stamped on all
their rifles enable researchers to cross reference with records
at the Buffalo Bill Center of the West Museum in Cody, Wyoming,
to establish the weapon had been manufactured and shipped in 1882.
None of which helps much to determine when the rifle was left there, except some time after 1887. If they could determine who the rifle was sold to and if he disappeared up in the hills...