I'm selling my 105 rear mech. It was taken from a brand new bike and has only been ridden 15 dry miles before being replaced with a long-cage one.
The mech's in excellent condition (it's still got the luminous packing grease on it). The only blemish is a tiny cosmetic scratch on the underneath which you can see in the picture to the left of the cable clamp. Jockey wheels, spring etc. all like new. Cheers.