It means that the leather is porosus crocodile, which is the best crocodile leather Hermes uses in its bags. Two dots stamp is for niloticus croc leather and a square stamp for alligator leather.
bagsmaniac: You can go to HermesGroupie's leather book. There is picture of Niloticus and Alligator leather.
http://forum.purseblog.com/hermes-r...ence-hermes-groupie-s-leather-book-49095.html