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Device for ascertaining the date of fertile days in the menstrual calendar

The device came in the book ‘The Fertile and Unfertile Days of Women and Their Definite Calculation,’ by Hermann Knaus.



Inventory number: 1131
Material: cardboard
Dimensions, in cm: 3 x 15,3 x 0,5
Date: 1953
Condition: very good
Artist: Hermann Knaus