Unlike some other items you buy, a date stamp on a Hermes bag doesn't matter a jot, there are so many chasing these bags and so few available. The stamp, to the vast majority buying Hermes bags from the store, is not even a consideration. You are so lucky to have a very hard to find bag purchased for you with love, don't let this non issue of a date stamp spoil it for you, be happy, enjoy and give your BF the biggest hug for being so wonderful!!!
You have a spankin' new store bought Birkin!!!!!!!
Merry Christmas!