Welcome to the forum, AZshot.

Lovely rifle.

In Victorian times (and quite a bit later) it would have been regarded as suitable for Roe deer, Blackbuck, Duiker and the like.

If the sling mount holes are non standard you could look for a silent sling with leather thong ends (or just make up a couple of loops with leather laces to fasten your sling strap to).

Parker-Hale used to make hooks with swivels attached but they tend to be noisy and could come unhooked at the wrong moment.