The Foundation Gate Keyway is an ancient locking mechanism installed within the final sealed gate of the Lower Eastern Foundation Sector. Constructed from heavily corroded iron and integrated directly into surrounding stonework. The assembly predates most documented Archive infrastructure. The lock was confirmed to accept the Salt-Worn Brass Key without resistance. This established the first verified connection between the recovered key and a physical Archive system. Spiral carvings preserved around portions of the lock match symbols previously observed within maritime records and the missing Submerged Doorway Sketches. During testing unidentified water movement was heard beyond the sealed gate immediately after key insertion. The sound ceased when the key was removed. The gate remains unopened and no internal inspection has been conducted.