Not a benchmark! Rather that is the Mt. Diablo Initial Point that controls all land surveys in Northern California and most of Nevada.
Thank you Gary. I'll correct it right away.It was the closest thing I could find to a benchmark on the summit..
Jason, my apologies! Never trust an anonymous Internet blowhard! (that's me) Your very nice photo is not the initial point. This is:
Please forgive me for being so pompous.
Maybe I should call it "Big brass tourist attracting benchmark type thing". :)