This is a letterbox, please don't take the stamp
At the GZ you will find a trail marker
If the color on the post is green - then the letterbox is located at
N39 03.202 W84 07.586
If orange then
N39 03.255 W84 07.625
ODNR Permit EF-04-14-24
See https://coord.info/GCARY9Y for parking and trailhead info
Here's a great park map https://drive.google.com/file/d/1vN-M0wnOxctzyuZbwmqZ-M6wVak81Z9Z/view?usp=sharing
You are looking for a metal water bottle by a massive tree.