The plaque reads:
During gold rush days a look-out stationed in a structure on this spot observed and signalled the arrival of incoming vessels. By adjusting movable arms high on a tall pole and by hoisting national colors, he indentified the nature of the ship arriving and alerted th etown below. After four years, in 1853, this novel signalling system became obselete through use of electrical telegraph.
This monument erected by California Historical Society July 20, 1961, on the occasion of the arrival of "S. S. Canberra" of the P & O Steam Navigation Company.
Original plaque replaced by the Coit Tower Preservation Fund and redidicated January 31, 1993 on the arrival of the "S. S. Canberra", world cruise 1993.
(Click the image to view a larger version.)