Letterboxing pre-dates geocaching as a location-based game. People who letterbox (letterboxers) have their own stamp and a journal of their adventures. They follow clues rather than their GPS to locate the box that contains a stamp and log book. Finders stamp the letterbox's stamp in their journal and their stamp in the letterbox's log book. A geocaching letterbox hybrid will have a stamp in the container as well as a log book. You may sign your name or stamp the log if you have a stamp.
This hybrid letterbox in Silver Mine Park starts at the monument at posted coordinates beside Silver Mine Run. It's down closer to stream level. Note the date on the plaque. Walk south on the paved path until you reach the Y intersection with the path to the left leading up the hill. Go up the hill. At the top of the hill where the upward path ends, turn right. You are now taking the high road south. Walk past the small building as well as the fence on the left. From this point, pay attention to things easily visible in the woods on the left side of the trail. You are looking for a concrete slab about 4 feet long and wide that has a foot tall metal object in it. It's about halfway along the flat straight part of the path. If you start to go up the next hill or get down into the open area, you have gone too far.
You are at the metal object and need two calculations based on the date on the plaque. The month on the plaque can be considered a number. That number can be considered an hour on a clock. And that location on the clock can be considered a compass direction. You will look in the opposite direction from the one indicated by the month. Opposite of month. How far should you go? Add up all the digits in the date that are not 9. Go that many feet in the opposite of month direction. This will NOT have you falling off the hill.
The container is a small flat camo'd box. It has a stamp, ink pad, and a log book. Please be sure it is closed securely before you leave the area. Do not take the stamp or ink pad.