This is a Letterbox Hybrid 
cache. There is a STAMP inside a Letterbox Hybrid, it is NOT an item intended for trade; the stamp is meant to remain in the box so that visitors can use it to stamp and record their visit.
Denver's Sanderson Gulch Trail follows the small stream for nearly 5 miles through several parks, offering a natural oasis right in the heart of a major city. Much of the paved route has an open feel, but there are trees here and there in the waterway's valley. Residential neighborhoods border the trail along its north and south sides.
Ruby Hill Park on the trail's eastern end is a notable highlight. The park offers a nice vantage point for viewing the city's skyline and has an artistic pavilion and plaza area with picnic tables, restrooms, and playgrounds.