For your consideration, here is an Outdoor Garden Hide A Key Made of a Rock and Recycled Prescription Bottle.  For hiding a key or other items out in your yard.  The bottle is waterproof.  The glue used to attach the rock is waterproof also.  The space in the bottle measures a little over 3 inches tall with a diameter of 1 1/4 inches.  Just push down on the tab and twist to open the bottle.  It will be mailed in a box for protection.  Item pictured is the actual item up for sale and comes from a non-smoking household.  (611.60p-.7bb)