I have hundreds of in person (yes, I went and got them myself being I lived in NYC more than half of my life) and would never try and resell them, I know they are real as I went and got them, however even when i put them up against what is on line, a good amount of them are not even close to others I find online from card companies. I find this because it depends on where and when you get them to sign. If they are standing and trying to sign a playing card or ball, its always in a hurry as they are trying to sign for many people and the sharpies I used to use is a thick line, not a thin line, plus they are standing up and not sitting, different arm angles and usually pushing against my back as a surface or using a magazine, its not the same resistance as wood. Plus, with the limited signing area cards come with and stickers being the norm now a days, do you really get a complete auto anymore? Most are shortened to fit the area, dont agree with me, go and try and sign your own auto on an index card then get a piece of sticky tape the same size of non card autos and see how you do, i have a long signature due to my name, not even close to being the same as an index card or even the bottom of a contract.
Steiner sports is one of the best at delivering the goods, used to visit them every few months in NY. Talked to them a lot before i hopped the pond to move here. They have a strict guideline on how things are signed, how its verified and documented. That is why they are so expensive because you know your getting the real deal. What your buying from them is their COA which doubles the price of the signed article. Now, just in case someone states that Steiner blah blah blah, yes, they have sold to new owners in the past, the original owners are the ones I dealt with, as i have been here for 16 years, so no idea if they have also gone to rubbish, but 16 years ago, there name was worth gold.
Its a nice looking jersey with an auto, if your worried about it, go and spend the 500 or 1000 dollars on the jersey with a coa where there was a witness to the autograph, like Steiner, if not, enjoy what you have, put it on your wall and just be happy it adds to over all man cave, at least the seller here is telling you there is no COA, its not a COA which was made in word and marked up to look real.
As for signed jerseys, i have 4 from D and A card world, I find the COA's that come with them about as legit as nothing, again, nice jerseys with some auto on them.