The instrument is very similar to Epact 86254. It is composed of five copper superimposed discs, the central of which has a handle in the form of a double dragon's head. On one side of the dial is a brass arm with a pierced and engraved lunar volvelle, showing the phases of the moon. There is also a perpetual calendar, showing the total days of the current month, the length of the night and of the day and the ruling planet for the current day.