It is a sea spirit, a drop of ocean in a wooden box. I made it as a gift to my sister who loves the sea, but who has recently had to move (temporarily) to a city.
This, I hope, will help her bring the outside, inside.
The inscription on the lid is anglosaxon, taken form the Bosworth-Toller (my favourite book in the Bod when I lived in Oxford).
It reads "I come from the arms of the sea".