Tedk said

win4575 said
Bottom swivel on an original Winchester sling.  Top swivel is a reproduction.  The obvious difference is the sharper bend at the open end of the original.  There are several other subtle differences also.

  

Thanks for posting. The hook itself is also much more refined and pleasing to the eye on the original, while the hook on the repro has a crude, blocky, unfinished look. The top of the ‘ball’ on the original is not solid and has a separate round piece of metal that is flush with the ball. Does the repro share this characteristic or is the top of the ball solid? Thanks again.  

Again, another great and informative reply with picture.  Thanks!