What was Hitler’s ‘first-rate Jews’ list?

The "first-rate Jews" list included gifted musicians (and possibly their family members), who were protected by Hitler. In context, we can infer that Paul's father is referring to the fact that Keller must not have been on the list, as Keller's wife and son were taken to the concentration camp and killed. Keller also registered as a Jew (he was not) and spent time in the camp.