A brand of hope in wet concrete, and questions

I've seen this symbol many times in my life but this one caught my eye this weekend on a decaying sidewalk in Norman. I wondered about the people working on that Depression era crew long ago  in Oklahoma in the residential neighborhood of small frame houses. How hot was it? How long had they been working that day? Where were they all from? Which hands were assigned to place this symbol, this brand, of hope and three meals a day in hard times, in this concrete? They're all dead now, but still I wonder.
Then it occurred to me that I've never seen the tool that was used to imprint this brand of hope in the still wet concrete. Was it like a cattle brand? Was it a badge of honor and experience to be selected to place the mark of a long day's work in something that would last? Who designed the tool? Where were they made? What were they called? Have they all rusted away, or been melted down for metal in the war years? So many questions, unanswered in the years.