An 18th century German perpetual calendar of disc form with the days and date on one side and...

An 18th century German perpetual calendar of disc form with the days and date on one side and inscription " Calendarum perpetuum", the side with six apertures and the titles: Monath, Tage, Sonegehet auf tages lange, nacht lange & Himmels Zeichen, unmarked, probably mid 18th century, 1.75in (4.5cm) diameter.