Welcome to the Preble County Courthouse. The coordinates will take you to a historic marker to tell you about it and help you get the coordinates to the final stage of the cache.
Final is a quick park and grab less than half a mile away at N39 AB.CDE W084 FG.HIJ
A&B=Number of Courthouses erected on this site (PLUS 1)
C&D=Number of letters in the word of what is first listed as contained inside the copper box.
E=Middle Marker Number (bottom right).
F=Month Cornerstone was laid.
G=First Marker Number (bottom right).
H&J=First Marker Number MINUS Last Marker Number (bottom right)
I=G
You can validate your puzzle solution with certitude.