This "is the original fog-warning bell that sat at the end of the landing pier.
Years ago, it disappeared from Angel Island and was found in a San Diego junkyard.
The two-ton bell was restored and returned to the island, first as a marker
at Ayala Cove and later to its present site in China Cove."

- From americansall.com


(But see the more-likely actual story, as told in the Comments area.)