As I promised yesterday, here's a Pasadena sidewalk stamp. This one's from contractor J.E. Haddock in 1928. A closer view is below.
You find these around town, from different contractors. They're not everywhere, just the older neighborhoods. Further study would tell us when these were most commonly used. If you know, I'd love to get your comments. My guess would be this began after 1900 and stopped before World War II.