The designs of Cor Dijkman Dulkes were:
PH-COR: GB-25 Dijkhastar with the name standing for DIJKman Dulkes, test pilot van der HAm and co-designer STAaRrgard. This first PH-COP was an illegal aircraft as it was built w/o knowledge or permission of the Dutch CAA. However, it did fly, albeit only once (that is the of course official version....)!
PH-COR: Dijkhastar II was the second and this time official and is the a/c in teusje`s picture.
PH-KOR: Dijkhastar III is the red one and basically had nothing in common with the Dijkhastar II.
PH-CDD: Dijkhastar IV: This was an amphibian which was nearing completion when Cor died and unfortunately never flew.
The illegal PH-COR was a single-seater, the second PH-COR, the PH-KOR and the PH-CDD were two-seaters.