Greg Tucker is one of the more respected autograph dealers in the community. His stuff is legit. The only problem is that his COA is easy to forge, so a lot of unscrupulous dealers are using his COA to pass off their junk as real. I have an autograph that I purchased from Greg Tucker and it has his hologram sticker on the photo (in addition to the accompanying COA). I'd question whether or not the autograph was actually obtained by Greg if there is no sticker.
My reply comes a little late.. Here is a picture authenticated with sticker from OA also from Greg Tucker . Sold on ebay in 2012. Your photo and that signature looks identical to me.
PS. Sorry can not attach the picture saved from ebay ..