There are hundreds of football/soccer jerseys/shirts on the market and it makes harder for the fan to tell the difference. As a collector and seller of jerseys over the years i have been able to spot out the differences. Lets begin with the Adidas jerseys,
1) Most dealers/wholesalers selling authentic adidas jerseys will have them presented in their official adidas bag.
2) The jersey if brand new will always have the sticker/barcode which states the size of the jersey, the team,if its away or home jersey.
3) All authentic adidas jerseys will have an inner tag on the jersey which states the date of manufacture on the first line, on the second line will be a 6 digit code, as seen in the 2nd photo this code should always matches the 6 digit code on the top right hand side of the tags.
4) A lot of the fake jerseys only come in one size XL and if they come in over sizes they wont have the original tags stating the size, it will alwayssay xl on it with a different size tag sewed on next to it as seen in the following pic.
5) When you have a good look at the inner tags the quality of the font and spelling will always be of lower quality on a fake jersey.The following picture has a photo of the fake jersey and the real one, at normal observation they both look the same however at closer inspection you can see that there are mispellings on the left photo, after the 100 percent symbol the words polyester are on 2 seperate lines and not next to each other,as in first pic, accents missing on certain languages, and the picture of the 40 degrees celcius is missing the celcius sign and the degrees symbol.
There are many more give aways for example if its a climacool jersey then the tags should say climacool not just simply adidas.
If its a uefa champions league jersey then the shirt must come with the adidas tags plus the champions league tags. For example in the first photo this Bayern UCL jersey comes with the adidas Bayern Munich tags, the Champions League tags and the Bayern Munich club hologram tag. In the 2nd photo it has the white barcode sticker on the reversal stating it is a FCB jersey from the UCL and in L/S.
The majority of fake jerseys on ebay come from far east asia mainly Thailand. So if the seller does not keep their stock they are mainly dropshippers and their shirts are shipped from Asia mainly Thailand then this is a give away they are copies. This is mainly used to keep customs officials of the sellers back by having them directly sent to the winning buyer the seller has wiped his hands clear of importing counterfeits as his/her name is not on the senders details only the companies is, who is based in Asia and chasing them would be harder for customs officials then a national importer.Also you will find that most of these sellers dont combine postage or charge high postage costs also for the same reasons. If the seller were to import these jerseys and resell them in their country then sooner or later on inspection their goods would be seized by customs officials and they would face fines for counterfeit importation plus being chased up by the trademark owners.
Official Jerseys with players names and numbers are hard to obtain and expensive so sellers that are selling a lot of jerseys with every player and name available at low prices are mostly fakes. Also these sellers usually offer to have your own name and number placed on the jerseys too!
Mainly if your seller cant provide these assurances on their product then it is most likely they are selling a fake.
I will write another guide for nike jerseys when i next have spare time, but the same principles apply to most jerseys, ask for bags, tags with barcode stickers on the reversal of the swing tags always unless they are not new.