Card authenticity and counterfeits

I have recently purchased and recieved 6 Sandisk Extreme 80MB/s 32GB cards from Amazon UK direct (not marketplace or reseller but Amazon direct).

I wish to verify that the card are authentic Sandisk cards and not counterfeits. But there appears to be now way to do this.

On a close inspection all 6 cards have the same number printed on them which concerns me that they maybe counterfeit.

I have tested the cards using H2testw and verified that the read and write performance on all cards is 40MB/s and 70MB/s (respectively) and all areas can be written to. ANd performance indicates they are working correclty.

However as all the cards posses the same number I am still concerned that they may be counterfeit. I have contacted Sandisk support and await a response anybody here know how to verify authenticate Sandisk cards?