This signal, mounted via double guy to a metal pole, is located Highway 50, near its junction with Cirugu Street, a few miles west of South Lake Tahoe.
Correctomundo. An old clamshell with one of those "cobra hood" cutoffs that were so popular with CalTrans back in the 60s. I drove under that signal & light as a kid. Actually I should say "rode." I didn't have a driver's license back then. Of course the signal back then wasn't a 12-12-12 either. I think it was an old Econolite 12-8-8.
CalTrans pretty much changed out all their mast arm signals to 12-12-12s to go along with the new MUTCD specs. In fact I'm afraid that 8" signal heads are going about the same way as incandescent and MV street lights.