This neat 4-Way traffic signal is definitely one of the rarest streetlighting/traffic signal items in California, since 4-Way heads have not been popular in California, and in fact this is is the one 4-Way (aside from a similar 3-Way one in a different town) I have ever seen in CA! Span wire signals have traditionally been rare in California as well, but occasionally a box span wire signal hung on wooden poles can be found on US/state highways in rural parts of California.
This signal was found on Foothill Blvd in Cupterino, CA, and the photo was taken in 2001. But unfortunately this signal have been replaced by a standard California steel mastarm assembly using curved mastarms on poles which also hold streetlights above the signals. There goes another span wire in California, and that 3-Way signal (in Monterey, BTW) is gone also.