This miniature is an abacus or tidal calculator. It was one of the sides of an interesting instrument that was used to navigate and figure the time of the tides. On the back side, it has a Wind Rose.
The tides, with their constant change in the water level, greatly affect navigation both in harbors and for fishing.
The original piece was one of the earliest British Renaissance instruments. Signed by Humphrey Cole it was a Nocturnal and Tidal Abacus (1570). Currently, this instrument can be found in the British Museum, London.