You wouldn't think the historical plaques that you'll find at interesting spots, affixed to boulders and other weighty objects, would do any moving around. But this is the second one we've caught perambulating. (See the other at GCWN2B.)
The original monument to Portolá's November 12th camping spot was placed in 1932, but likely removed during the construction of Interstate 280. Curiously, current USGS topographical maps still show its original location, at approximately N 37 25.611, W 122 24.959, which is now along the frontage road. A new version of the monument was placed here in 1976, as part of the nation's bicentennial celebrations.
The new plaque is recessed into a massive serpentine boulder. Serpentine is California's state rock, very appropriately as it is a metamorphic rock unique to earthquake faults, where it is formed under immense pressure in the depths. This specimen has a very nice display of the 'slickensides' polishing that often occurs on serpentine as it is ground in the fault zone.
The hide is a mag key holder in an obvious spot. There can be a lot of traffic at the trailheads here, so please be stealthy if necessary and rehide carefully in the original spot so the container is not visible.