Frits David Koetser went to the textile school in Enschede and temporarily lived with the De Jong family. During the raids in Enschede he was arrested together with the son 545826.
For a biographical note see: H.E. Dominicus, Mauthausen. Een gedenkboek (2e herziene en uitgebreide druk; Amsterdam 1999) 83.
This person is commemorated on a memorial in Enschede. More information on this memorial can be found (in Dutch) on the website of the Nationaal Comité 4 en 5 mei.