The only aircraft still in existence which has been designed and built by Koolhoven, is this F.K. 23 Bantam fighter. It dates back from 1917 and is now on display at the Aviodrome aviation museum in Lelystad, The Netherlands.
Another great participant of the 2004 airshow at Lelystad airport was this Ju-52. This airframe was found somewhere in the UK in the 1990's and was fully restored to airworthy conditions.