Thanks to clues from an astronomy historians' mailing list I have now located a second specimen of the #perpetualcalendar in question at the Deutsches Museum in Munich - with the context I wanted: https://digital.deutsches-museum.de/de/digital-catalogue/collection-object/39190/ (more on the life of the maker https://www.rijksmuseum.nl/nl/collectie/RP-P-1907-1142 can be found in https://www.astronomie-nuernberg.de/index.php?category=personen&page=henning-vb while Dutch counterparts of the same calendar have been on the auction block at https://catalogue.swanngalleries.com/Lots/auction-lot/SCIENCE--PERPETUAL-CALENDAR--Henning-Veit-Balthasar-Eeuwig-D?saleno=2127&lotNo=309&refNo=590688 and https://onlineonly.christies.com/s/science-natural-history/dutch-calendar-55/130608).

Complex #PerpetualCalendar made from cardboard, found in the #museum of #Altena Castle in Germany (exhibit B 1445) - which sadly provided no context about age, provenance or users.

@glennf Somewhere in the house is a 'perpetual' monthly calendar from that era containing an adjustable printed metal plate inside a brass display cover with an open area to reveal the date numbers on the plate. The plate could slide from side to side to adjust the display on the front, and the back display was an array of something like 30 years of months, and sliding the back of the plate to the appropriate month would display the correct calendar on the front.

#PerpetualCalendar #calendar