Originally posted by HomeMadeSin I've never claimed to be the sharpest tool in the shed, but yes. In case you are still unconvinced, per the manual (props to M. Butkus of cameramanuals.org): "In order to obtain certain effects, you may screw ZEISS IKON color filters on the thread (4) of the lens (Ø 27mm)."
Sorry to have offended you. I was hoping to save you some effort. It is not unusual for unusual filter sizes/designs to have a filter holder as an option. At least that is how it is with my vintage folder. Since you already knew that you know where to look. If you can determine the pitch, you might be able to have an adapter made. There are also several online resources that specialize in hard to find filters and adapters. Google is our friend. Good luck.
Steve