The patent date is probably US patent 188,775 “Fire-Proof Safe” by William H. Butler. This only establishes that the safe was made after March 27, 1877.
In 1879 the agent was Thomas Brett but that could easily have changed over the years. If you have access to a good library in Ohio, you might be able to find some Cleveland city directories which might list Diebold agents. I tried Google Books but was not successful.
