a very old bus, almost entirely wood, and the body is nearly complete, but it's parted ways with the chassis long ago

Above you can see the condition of the roof better.

I wish I remembered more, but I can't recall anything. If you'd like to know more, you can get ahold of the Motor Transport Museum http://www.motortransportmuseum.org/ 
and see what they can tell you. I'm sending an email myself, and see what they can tell me (which I should have asked when I was there but was stunned at the variety of things to see)

"Any and all photos taken on the museums property must include the wording: "By permission of the Motor Transport Museum, 31949 Highway 94, Campo, California, web site: http://www.motortransportmuseum.org"