When DH picked up his items at Artcurial, he spoke to the woman in charge of the Hermes auction and learned some interesting info. The owners of Artcurial are close to the family running Hermes and it is the largest H auction in Europe. They get some of the items from H itself (how and which ones I don't know), and run most of the items by them for authenticity.
He still doesn't think that he paid too much for his towels.
He must REALLY love the towels!