Winchester Model 72 question

something does not look right with these swivel studs, maybe someone familiar with these can tell if they are factory installed or non original, that is first I seen one on magazine tube, thanks, this auction is coming up http://i465.photobucket.com/albums/rr19/marcus396/157.jpg
http://i465.photobucket.com/albums/rr19/marcus396/157-5.jpg