GSC convex tablet stamped 68L520, set horizontally on the wall of a rock of the west right-of-way of South Street, 82.0 m south of Montgomery Avenue, 1.1 m south of the lowest step of a stone staircase. The marker is located 0.33 m from a beacon on a rod, 6.20 m from the centre of South Street, 1.50 m from the stone wall, 0.43 m above the ground and 25.65 m from the southwest corner of street address 158.