I was doing some research on C.C.W. Haun, one of the contractors whose stamps I found yesterday in San Francisco, and discovered this photo, which is part of an incredible collection of air vent by Flickr user some.accesss. It's interesting that this contractor, who advertised "Art Stone" in his cement stamp (below), also did plumbing work. Also interesting: the cement marking listed C.C.W. Haun's address at 413 28th, while the air vent shows it at 313 28th.
