It appears that there were two contemporary tanners, both called Isaac Nothmann, one a master tanner by 1866, the other an apprentice tanner when he died in 1873. However, other sources lead to the conclusion that despite the differing professional status the records all relate to the same person.

The apprentice tanner
The JRI-Poland record of Caroline's 1874 marriage names her parents as Isaac Nothmann and Rosel Wolff, and describes her father as "Apprentice Tanner deceased"; this appears to sit well with the JRI-Poland record of the death of Isaac Nothmann, "tanner (journeyman)" in 1873 aged 53 years; the record is from Myslowitz, but gives no other information.

The master tanner



In 1846 Isaac Nothmann, born 14/09/1817, a tanner (Gerber), son of Loebel, and his wife Eva geb. Tichauer moved from Langendorf to Eva's home town of Meseritz (O/S), Kreis Pless, 15 miles south of Katowice. The records of their departure and arrival both cite family number 2507 which makes Isaac a descendant of Schaye Nothmann. (The registration numbers of Schaye and his contemporary family members are given on his father's page.)

In 1866 Louis Nothmann, infant son of master tanner (Gerbermeister) Isaac died in Przelaika, some 4 miles north of Katowice.

The confusion
Gustav's death certificate places his birth in 1844-45 in Przelaika, so he was probably a (half-)brother of Louis and so a son of the master tanner. muzeumzabrze.pl identifies Gustav's mother as Rosel Wolff who, according to Caroline's marriage record, was married to the deceased apprentice tanner.