This octogonal model is based off a design by Charles Bloud of Dieppe in France. Inside there is a horizontal sundial, with a compass. On its vertical table, lunar volvelle for telling the time at night (more info below). The cover features an equatorial (or equinoctial) sundial.
It comes in a beautiful case and has a booklet with history and instructions for use.
Two options are available for the cover: one topped with a colored paper, the other an etched brass plate.
How to use the lunar volvelle:
The lunar volvelle converts the time as read off the sundial, cast by the shadow of the moon, and converts the reading the correct time (within an hour or so, these could not be as accurate as a sundial). Set the point on the volvelle to the current lunar age (1-29, with 1 being the new moon, and 15 being the full moon). The current solar time corresponds to the time indicated by the disc. In other words, the dial simply offsets the time to correspond with the precession of the moon.