Trestle Park is an historic railroad trestle site established in 2012, commemorating the logging days of 1882 to 1887. There is an anchor there that was discovered in Houghton Lake, an informational kiosk, pavilion, and play area for the kids on the shore of Houghton Lake. During the summer they have Concerts in the Park, as well as other fun events.
The coordinates take you to a Michigan Historical Marker describing the history of the local area. One side is titled "Prudenville", the other is titled "Roscommon Lumber Co." To find the coordinates for the final location, you need to get some numbers from the marker.
For the north coordinates, take the 2nd and 3rd digits of the historic site number, and add them (as a 2 digit number) to the posted north coordinates. For the west coordinates, look at the "Prudenville" side, and take the first 2 digits (again as a 2 digit number) of the decade in which the area's next economic surge came, and add them to the posted west coordinates. You will not have to leave the park to find the cache.
The container is a small peanut butter jar that blends in well. Please make sure it is replaced as found so as not to be muggled. Stealth will be required as this can be a high muggle area. You will need to bring your own pen or pencil.