Originally Posted by UThomas
R stands for Reject not rental I think. As in it was out of tollerance. At least per www.customcockers.com
My refurbished trilogy sport that I got for pretty cheap has a 'R' stamped on the side. (see this picture
between the vertical ASA and the grip frame).
As for the eBay auction, all questions are supposed to be asked before bidding. If the 'R' was obvious in the ad's description or photo, there was nothing hidden.
The best you can do is give them bad feedback as a nonpaying bidder and relist it. You can't force them to pay.