I am amazed with Frederic Ives Kromskop Camera Images. Do these cameras color filters and their viewers color filters matches with todays RGB Filters ? How old timers prepared such filters ? Is there any spectral comparison ever made ? Is it possible to repeat old coating technology or are they colored glasses but not coated ? Where to look for that research ? If I find the filter manufacturer, may be I can go from patent route. If I find the spectral curves , I can order the coatings.