Johann's birth year was calculated by taking the age of his daughter, Elisabetha, on her wedding day, 25 (likely turning 26 that year) in 1848, and subtracting 25.
1848-26=1822 (Elisabetha's estimated birth year) 1822-25=1797 (Johann's estimated birth year)
http://portafontium.cz/iipimage/30061344/domazlice-50_0030-o?x=473&y=115&w=344&h=155
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