Perpetual Calendar and Altitude Sun Dial

This vertical disc dial has two sides: an altitude sundial and a perpetual calendar, which is the one depicted.

The calendar consists of three rotatable discs set on top of the main disc with a date scale and a lunar age scale among other features.

Made in France (1650-1700), is at the National Maritime Museum, London.
This vertical disc dial has two sides: an altitude sundial and a perpetual calendar, which is the one depicted.

The calendar consists of three rotatable discs set on top of the main disc with a date scale and a lunar age scale among other features.

Made in France (1650-1700), is at the National Maritime Museum, London.