I think the swivels are the ones Parker Hale sold. If that's right, they should be right for that rifle if the delivery date of 1957 on the paper in your photos is correct.

I'm not sure about the sling, but it looks of that time also.

BTW I saw the rifle originally came with a Nickel 2.5X scope. It's a shame it's not still with the rifle, as they are wonderful sights.

Dad just gave me his old Nickel 4X, which he bought in 1959. It needs a complete rebuild, but I have located a gentleman up to the task, and then I will mount it to my Mauser 7X57. It will be nice to hunt with the scope my father looked through as he shot several hundred deer.