This is a Letterbox Cache. The cache container contains a stamp, that is not a trade item. The stamp must remain in the container. You are looking for a small Lock N Lock.
GZ will bring you to a small rock pile, the container is covered by one rock. Since both Milli and I hate these hides, she was insistent on adding a hint. The rock you need to move is in the photo below. Moving numerous rocks, and not replacing where found may result in a buried cache container.
Remember, you only need to move one rock.
How many will it take?
Zbir bar ebpx bayl - Frr Zvyyv'f Cubgb Uvag
(Nobhg 3 ebpxf bire sebz Zvyyv'f evtug rlr)
Rqtr bs gur tenff.