This stamp is on the west side of North Clemens Avenue, at the intersection of Fernwood. The date is a little hard to read in the photos but I believe it is 1980.

I haven’t been able to find anything out about E. Harmon. My best lead is an obituary for Earl Harmon, Jr. of Lansing, who died in 2018 at the age of 75. It says “He was is (sic) concrete construction having started and being a partner of M & M Concrete in Charlotte.” Maybe he stamped things under his own name before forming M & M. Unfortunately, that’s all I have on this one.