Jacob Viskoper was a son of Israel Viskoper and Rachel Huisman.
Haags Gemeentearchief, overlijdensakte Jacob Viskoper (C1779, 1951)
In addition, a Jokos file (number 2599) on this person is at the Amsterdam Municipal Archive. Access is subject to authorization from the Stichting Joods Maatschappelijk Werk.