This Challenge cache is NOT at the posted coordinates, see waypoints for Final Coordinates.
You can sign the log at any time but in order to log a "Found" on it you must meet these qualifications:
Fill your D/T matrix with 81 different Counties.
You are welcome to find this cache before you qualify, please log a "Write Note" if you do. Once you qualify for this challenge, you can change your log to a "Found it".
Here's the checker:
Many thanks for the inspiration carnigrewal - GC7C9XE