This cache is a small lock n lock cache with a starfish stamp inside. The logbook was also specifically made for this cache.
You can bring your own stamp pad if you want but there is already one in there.
This type of letterbox is the first of its kind as far as I know.
Please do not take the stamp or stamp pad, they are not trade items.
Clues:
Hope you enjoy this one-of-a-kind letterbox. Hope this new experiment will be successful!