First off, I think this thread is in the wrong section, it should probably be moved to the Reputation board.  You can move it yourself, there's a button at the bottom, left hand side of the page.

Second, anonymousminer (like most of us) is very suspicious off-site sales links.  These are very commonly used by scammers, who use new accounts to spread their links around the forum to lure unsuspecting victims.

Your suggestion to send to a reputed member first may help you.  Giving out a "vouch" copy or two may also help.  The trouble is with your type of sale one key can be good and the next could be a scam, no one really knows.  The best thing for you to do is sell your keys here, doing the whole transaction through the forum without employing off-site sales links.