Whilst I urge our members to not bid on anything that vague, I can't help but feel he might actually be legit.
Always worth PMing him and asking what the 'extra item' is - get it in writing before bidding. If this sells I have the feeling this could prove popular before ebay put a stop to it.
I asked the seller the obvious question. If someone buys this and then finds an issue with it, the seller gets an easy out as there will be no sympathy from Paypal.