County of sign: Cooper County
Location of sign: 2nd St. & E Morgan St., SE corner, Boonville
Looks to me like something else was written at one time under this name.
The F. M. Stamper Company was a large company with provide produce and meats. The main office and owner was in Moberly, MO and when F. M. STAMPER passed, the company passed on to his sons.
In the 1940's they had labor issues, and you can read all about it here: Case Text