[cueball44]

Originally Posted by Malcolm G

Yes I have seen one and it was explained - but I've forgotten the details so not sure if this is all correct.

Basically comes from the days of sail when the helmsman was unable to read or write and make a proper record. They therefore used this board, which has the points of the compass in eight concentric rings and below a means of roughly recording when things happened, or were supposed to happen.

30 minute sand glass was used to record time, bell rung and peg placed in board - All cleared at end of watch.

Early navigation device. Correct.