1700 block San Pablo Avenue
This is the building that Piedmont Piano is in, but at the other end. Presumably the Gray Bros. were the overall contractor. “A.S.P.” stands for Artificial Stone Paving, a common name for concrete formulations in the late 1800s. The Schillinger Patent was the impetus for a major court case in 1894, Schillinger v. United States.
As of 1897 the Gray Brothers operated two San Francisco traprock quarries, at 26th Street and Douglass and at Green and Sansome.
Oakland Underfoot 
26 May 2012 at 10:42 am
I found another of these on 12th Avenue near E. 20th Street.
22 February 2024 at 1:20 pm
I’ve found two of these Gray Bros. marks in Alameda, most recently this morning when I saw one on Ninth Street near San Antonio. Saw another awhile back on Pacific Avenue near Sherman. Any idea of how late they might have been using them?
20 March 2024 at 10:00 pm
Found this site and reference while researching a quote from ‘Stairway Walks in San Francisco’ by Ada Bakalinsky first published 1984.
The book refers to the Sansome and Green Street quarry as being owned by The Gray Brothers Artificial State and Paving company.
No idea which is correct.
All the best
Tony
21 March 2024 at 1:48 pm
The FoundSF site has posts about all three Gray Bros. quarries in San Francisco. I should note that the photo at the end of the Corona Heights post shows the Oakland stamp, not one as claimed at Minna Street. The others were in Noe Valley and Telegraph Hill.
To answer Ken’s question, the company apparently folded in the late teens, after George Gray’s murder.
As for Tony’s comment, it’s clear that Bakalinsky was wrong, or just guessing. Here’s an 1895 California Supreme Court case with the company’s correct name.