7558 Greenly Drive
Kemble drew the date underneath, rather than inside the stamp here.

This mark, from Howard Avenue in Piedmont, documents two things. First, it shows that distinguished sidewalk maker Ed Doty held “Master Concrete” number 13, in addition to numbers 16 (1937-38) and 17 (1938-45).
Second, it shows that Doty switched from this stamp to the curved configuration, which incorporates the Master Concrete bug inside, some time between April and September 1937, when he used Master Concrete number 16.
1437 85th Avenue
This is the second example I have from the mysterious A. Nelson, and it confirms his name. I think he was very likely the mysterious Albert Nelson.