While hiking near Lake Chelan (Washington, USA), I noticed this item affixed to the tree located at 48.150978, -120.493732:
The tree in question is a short hike from a boat landing and right off a trail, but the area overall is fairly remote (designated wilderness).
I was unable to find any markings or other identification clues on the object. It appears to have been placed a while ago, as the screws holding it have been pulled almost completely out of the tree. The item primarily comprises a white, ribbed, rounded rectangular prism approximately 7x5x6".