The Hook type swivel with the large eye bolt in the stock was just an early Quick Take-Down sling attachment.
They do have a rather classic look. They do rattle alot. They do mar the wood as the hook can rotate to nearly any position.

The 'Quick' in quick-take-down doesn't always apply either.
Getting the Hook out of the Eye bolt is not always a simple, easy operation. The hook is generally quite robust, you want it to be so it doesn't bend or break.
It should be spring tempered so it snaps into and back out of the eye bolt again.
Not all of the ones made today have those features matching up to allow a simple mounting and dismounting of the hook from the eye.

But I still like the looks..

I must admit I have never seen the use of the leather only attachment to the eye.
Seems like a 3/16" piece of rawhide lace looped through the stock 'eye' front and back is quite small to depend on carrying the weight of your prize rifle through the field.
As long as the rawhide is knotted and drawn tight so it doesn't come undone as the article says to do it fitting it up,,it's not a QTD system anymore.
Just put regular, small non-QTD swivels on the rifle and a leather sling and be done with it. At least this can be taken off if you really need to or wanted to.
It doesn't have to be a bulky Military type setup.