On the Xbox Live Marketplace, every piece of DLC has a numerical ID. Some modders and archivists discovered a bundle ID labeled "103" that contained the Gold Edition content but was only available for 48 hours via a specific QR code at conventions. If you see a redeemable code for "ACR GE 103," it likely unlocks The Lost Archive plus the (actually a Brotherhood asset ported over as a pre-order bonus).
: Adds a puzzle-platformer campaign for Desmond and unlocks: assassins creed revelations gold edition 103 exclusive