Hi,
About your question for the validation keys, I'm honestly said that, the rubber does not have validation key seem I bought it just like on the picture that I provided.
For your information, I bought it from prott.cc for $130 including shipping.
The prott.cc admin said that the rubber dont have any validation key, because the supplier of the rubber who were hand over the rubber to him was taken freshly from the sole DHS distributor. You also can noticed that there are no series number on the sponge instead of only the thickness and degree of sponge were printed on the sponge.
You can judge by yourself about the authenticity of the rubber.
But, for me all of the rubbers that I bought from the website are real and very excellent in performance especially H3 national rubber.
You can have a tour to the prott.cc website and then you will noticed that some of the rubber in the special rubber segment dont have validation numbers and some of them have it. I dont tend to promote the website, but just sharing what I had experience from purchasing some of the online table tennis shops.
Cheers.