I found this one the internet
"One of the first pieces of equipment I noticed was this 1954 Euclid S7 scraper. Powered by a 4-71 Detroit Diesel attached to a 5 speed manual Clark transmission this green machine has a 7 yard capacity."
Also there was a note that a person found a maintenance manuals for S7 dated 1958
So I believe it is at least 1954 maybe earlier.