According to the "Sterbebücher" (death records) of Auschwitz, Iaaäc Beesemer was murdered there on 31 August 1942. This date is different from the official date of death of 30 September 1942 as determined by the Dutch Ministry of Justice after the war. For the time being, the website joodsmonument.nl, only list the dates of death, as published at the time in the "Staatscourant" by the Ministry of Justice.
The date of death according to the Dearh Records (Sterbebücher) of Auschwitz
The official Dutch certificate of death from the A-register 46-folio 52, nr 300 dated 18 August 1950