How to know Legit signed items from counterfiet ones?

[questate]

Well, I got a question here. I am an avid collector of games but somewhat new to collecting signed copies/editions. How can we determine a whether the item is legit or counterfiet. Here is an instance that happened with me today.

I was bidding for this item:

http://www.ebay.co.uk/itm/3208416811...84.m1497.l2649

I put my max bid. I asked the seller if there is anything to state the item is Authentic. here was his reply:

"Authenticity of the item? I don't understand? I have provided the pictures of the items sent to me. I work for the video game industry and I constantly get sent these type of items all the time.

Yes this is from Naughty Dog, and Yes these are authentic. I previously auctioned off this item however the original buyer did not pay and I had to file an unpaid item strike".

I won the item. I put the question on the thread RARE STUFF found on eBay (or elsewhere) and luckily for me Jugo confirmed in time that the seller 'feirce products' do sell legit goods.

However, is there any way to know whether the signatures on signed items are Authentic?

(Apart from asking the signatory, in which case ofcourse you would get the item personally signed, no need of ebay there!)