German translation: Privatkunden-Wertpapiergeschäft
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Explanation: I'm English so the following is only a hint, although I do sometimes translate into US English for German customers.
If the context is US banking, it means he sold securities (Wertpapapieren, Schatzbriefe, usw.) to the bank's retail customers (Privatkunden).
If the context is different, please supply more background!