Attest

at·test

verb\ə-ˈtest\

To affirm to be true or genuine; specifically : to authenticate by signing as a witness.

In the show "Pawn Stars" people are always bringing Rick old stuff that could be very valuable BUT at times it is risky for Rick to buy things when there are a lot of fakes made. Because of all the fakes, Rick gets the items attested to make sure they are REAL.