Vintage Rolex Authentication

[uhr.haus]

I have found a few vintage looking Rolex watches, a mens two tone daydate, and two ladies datejust. From the pictures I've seen there is significant wear and bracelet stretch to date them as pretty old.

I am wondering when I do inspect them what should I look for to validate authenticity. The owner found them in a larger lot purchase so is unsure as well.

Thanks!