To eliminate some concerns as to the authenticity of an autographed item, I include in most cases, what I call a POA (Proof Of Authenticity), which usually is a copy of the flyer addressed to me and the page listing the artist as a scheduled guest. While I provide certificates for some items, my experience at conventions is that, the table selling certificates is far removed from most of the artists. As a result, the signing isn't witnessed by the sellor of the certificate, so how can this be guaranteed authentic? Another source of certificates are those printed up by the sellor who guarantees authenticity!!! Just a thought not to get hung up on certificates. I have been selling signed items on ebay since December 4, 1998. I haven't had any problems with authenticity in all that time! I personally guarantee that the signature is authentic, and was signed by the creator, witnessed by me.