Died aged 8 years 6 months, so born 1862. The death record is from Beuthen and notes that the death occurred there, but gives the residence as Tost. It names his parents as Isaac and Rosalia; it says that Isaac, a merchant, is deceased. The identity of his parents is a mystery: my tree includes cases of an Isaac Nothmann married to Rosael / Rosalie in the appropriate timeframe to be Oscar's parents:

Isaac Aaron Nothmann and Rosel geb. Wolff
Two factors oppose these parents:
1. Oscar's father is described as a merchant, whereas this Isaac was a tanner.
2. Oscar's father was dead when Oscar died in 1870 whereas Isaac the tanner died in 1873; however, it is possible that Isaac is a conflation of two contemporary tanners with the same name.

Isaac (J.J.) Nothmann and Rosel geb. Kornblum
There are no obvious objections to these being Oscar's parents apart from the gap between their children's births in the 1840s and Oscar's in 1862. However, if Rosel married young, being born about 1820, this need not be an objection.