The Peep Hole
Here we have a strange looking box with a door style spy hole in the front, take a look if you like but you wont see anything!!!
The finders need to bring a AA battery with them to place against the two protruding screw heads on the side, then take a look through the peep hole and hey presto you see a number!!!
The container will be supplied with a suitable waterproof box, log book. pencil and woodscrews for mounting.