In addition, a Jokos file (number 52600) on this family is at the Amsterdam Municipal Archive. Access is subject to authorization from the Stichting Joods Maatschappelijk Werk.
GenLias has the birth record for Samuel van Gelder:
Geb 08-11-1873 Groningen #1201: Samuel van Gelder g. 08-11-1873 Groningen (Philippus van Gelder, beroep Koopman en Judic Appelboom)