This is his certified signature on the press release of Héritage in 1992.
Compared to this, the one on eBay seems a bit... copied...?
There is a bottle of this (well two bottles - you know the hearts that fit together) currently for sale on Ebay. One bottle is autographed - probably by Jean Paul Geurlain ... how can I verify that it is his? Anyone ever seen his autograph?
I don't know about other people, but my signature does not look identical every time. It is more noticeable when some time (years) have elapsed. May be the medium used also contributes to discrepancies. If the signature is on a bottle, the surface is different than a piece of paper. Having said that, it is very difficult to figure out whether an autograph is real or a forgery. Does the vendor have good feedback over many transactions? Maybe you should send some questions and measure their knowledge. You could ask the vendor how he/she come to acquire this autographed bottle. If it seems to good to be true, maybe it is. The only autographed bottles I trust to be authentic are the ones that are signed right in front of me (as Kilian Hennessy has been kind to do).
Thank you Arwen and Mr G, I think I will contact the seller for more info. As you quite rightly say, signing a (curved) bottle is going to be quite different to a piece of paper... In the end, it's the perfume I'm really interested in so the autograph is just a bonus I guess!