I got this from a dealer at a Gun Show that used to be held in Greenwich CT years ago, it was a high end show, mostly SxS dealers and custom rifles upstairs and parts downstairs. The seller was strictly a Winchester guy, all sorts of hard to find stuff like this.

Sold as a package, 1-1/4" Super Grade swivels with 1-1/4" sling. Leather is supple, no cracking, brass hooks are heavy gauge.

$475 plus shipping....

Link to photos..

Is that a Winchester sling?

I was told it was when purchased but no markings.