This card holder replaces the original crappy cartons that the dutch blitz game comes with. It can fit 8 decks and it has a little spot for the instructions. I also have an onshape model if you want to copy it and edit it directly:
https://cad.onshape.com/documents/ec55f80ee2f9f4544da4daf0/w/d79f200018417cc9146ea820/e/e84632b25f642666cf8e78fd?renderMode=0&uiState=67bb281287b86d1ce39491ee
The author marked this model as their own original creation.