(A few people have pointed out that i had the captions mixed up for the pictures below. Sorry! And, thanks for letting me know. They're fixed now.)

Quite simply, nearly every Fred Perry polo I've seen on ebay is fake. I would recommend not purchasing them from ebay sellers at all, but if you must, there are several things to look out for:

1: Price - You're not going to get a shirt that costs 40 pounds when new for $9.99. If it's that cheap, it's probably fake.

2: Location - Stay away from sellers from Asia, especially Thailand. Nearly every fake Fred I've seen has been from sellers located in Thailand, often offering bulk orders.

3: What does it look like? - It's often hard to tell the quality of the material from photos, but there are several very easy clues that will tip you off to a shirt's authenticity. Real Fred Perry polos always feature buttons that are the same color as the dominate shirt color. So, a red polo has red buttons. A black polo will have black buttons etc. If you see a black Perry with white buttons, it's fake. Also, the classic Twin Tipped Polo should have a blue tag, not black.

I've attached several photos that illustrate the difference.

     
                The shirts on the left are real. Notice the incorrectly colored buttons and
                                                                                                   black labels on the shirts on the right. These fake shirts are currently for sale on ebay.                                                                                         
                                                                                                   I hope this helps.