Wouldn't trust him an inch. There was a programme on the TV not long ago about these type of eBay ads and they got Trading Standards to report on the authenticity of these allegedly signed shirts. They did a check against an original signature and there were huge differences.

The guy they were checking up on was signing them himself and by the looks of it, wasn't even bothering to remotely try and copy an authentic signature.

Email the bloke selling them and ask for a close up pic of the signature on the shirt... and then try and find an orig signature and compare. If you buy a shirt and the sig is different to the one he's sent you a pic of... it's fraud.