FYI - That's a quick opinion that they do not backup for certain. An actual written report would require you to send the actual item to the authenticatior and pay hundred dollars or more.
actually from Julien's terms
Julien's warrants the "Attribution", as defined above and subject to the exclusions listed below, of a lot for a period of five years from the date of sale and only to the original purchaser on record at the auction. If it is determined to our satisfaction that the "Attribution" is incorrect, the sale will be rescinded if the lot is returned to the Julien's Auctions warehouse facility in the same condition in which it was at the time of sale. In order to satisfy Julien's that the "Attribution" of a lot is indeed incorrect we reserve the right to require the purchaser to obtain, at the purchaser's expense, the opinion of two experts in the field, mutually acceptable to Julien's and the purchaser, before we agree to rescind the sale under the warranty. This warranty is not assignable and applies only to the original purchaser on record with Julien's. This warranty does not transfer to any subsequent owners of any purchased property (this includes without limitation, heirs, successors, beneficiaries or assigns).
so you can see that it's possible for Julien's to require two expert reports coming from people they agree upon. Getting an opinion would cost $100 + shipping costs per expert.