The ATM Cache
A good strong weatherproof box with just a narrow slit visible on the front.
Well with a suitable card in hand (Not one you would want to damage) simply insert to operate the mechanism, the door will drop open and you have another smiley on the map.
A suitable waterproof box, log book and pencil will be supplied along with woodscrews to attach to a post etc.
Youtube Clip - https://youtu.be/SaSLLBxeq6o