I just bought a grass green multipocket from eBay which I was sure was authentic until the seller told me that both the outside zip and the inside zip pocket zips were riri m8 and I thought the inside should be riri m4. Anyway I just rang Marc Jacobs in London and spoke to the manager and told him my concern and according to him you cannot tell a authentic bag by the zipper used. He said they all use different one and they change them often and he had never heard of this method of authentication before ever. He said the only way to tell with MJ bags is by the quality etc as they do not do serial numbers like other brands. So I am guessing mine must be real although a pfer has the same bag on eBay and hers is m8 for the big zip and m4 for the inside. Does anyone else have a MJ bag with both zips saying m8?