NameAnna Catharina Mertz 
Birth29 May 1757
Memo(her tombstone seems to say 2 May 1758)
Death6 November 1828
Memo(find-a-grave)
BurialForks Cemetery, Stockertown, PA
Parent-Proof notes for Anna Catharina Mertz
Catharina was baptized at Mertz Church 4 Jun 1757, the record says she was born 29 May 1757.
Consider these baptisms:
1. At Oley Hill: Henry Kime born 25 Jan 1785 baptized 10 Apr 1785 by parents Cathrine and John with Henry and Maria Elizabeth Mertz as sponsors.
2. At Zion Lutheran, Old Zionsville, Lehigh Co, PA: “Collections of The Genealogical Society of Pennsylvania Vol 251. parents: Conrad Marz (Mertz) and wife Margaretha, child: Georg, born: November 10, 1793, baptized: Feb. 27, 1794, sponsors: Johannes Keim and wife Catharina.”
I believe Catharina was Conrad’s and Henry’s sister and she married Johannes Keim.
I also wondered if there is any find-a-grave memorial for Catharina and I found Catharina Keim buried in Forks Cemetery near Easton. Catharina’s memorial, based on what seems to be a quite readable tombstone, says she was born 2 May 1758 and died 6 Nov 1828. There is no sign of Johannes in that cemetery but her tombstone does refer to him by name, presumably saying she was “wife of” Johannes Keim.
There is a slight discrepancy between her birth date of 2 May 1758 on her tombstone and 29 May 1757 on her baptism record. I have seen minor discrepancies like this in other cases and I am not troubled much at all by it — the dates “resonate”.