The Stamm Nummer (residence permit) of Loebel Moses Cassirer (age 58) and his wife Zerchen (probably a nickname for Zerchen), 1796 provides evidence of a birth date for Zerchen. The Stamm Nummer was a form of residence permit with fewer rights than a 'General Privileg' but more rights than the next step down 'toleriert'. Its existence was limited to Prussia between 1796 and 1812. Details of Loebel Moses Cassirer, his wife Zerchen Ruben, and their children Moses, Hirch, Gerson and Jacob, with their ages (28, 25, 24, 22 respectively) are listed.

The age given on the certificate for Zerchen appears to be 50, From this we may conclude that Zerchen Ruben was born in 1746.

We can view a Legat certificate for Zerchen married Löbel MosesCassirer at https://cbj.jhi.pl/documents/478919/0/

See also: http://genealogy.meta-studies.net/ZDocs/Stories/TwoFamilyLines