Compass Octogonal Brass

Any object that produces a shadow is potentially a sundial. The construction of a sundial will depend on the selected projection plane: the equator, the horizon, or a vertical surface.
Quadrants with a compass, introduced in the 15th century, were the first portable sundials.

This model has Compass Rose in the upper part with a needle to determine different rhumbs. On navigation charts, the 32 rhumbs are depicted converging on one side, while the other shows the rhumb over the circle of the horizon.