My guess is that because the slide projectors were made mostly from Strong's movie lamp house/follow spot parts stock, Strong built the special parts to order. I'd not be surprised if there were a model or 2 in the catalog that were never built. In all of the old movie houses I've worked in or visited, I don't recall seeing a slide projector still in an operating position in the booth - typically there was a 3rd projector for the trailer reel when the feature was an anamorphic print (no lens swap). I do recall one old projectionist who told me "there used to be a slide projector there" when he pointed to the #3 machine.Still have no definitive info on the projectors. I do now know Strong did offer them as part of there catalog but it seems not all that many made it in to the market. So that is why they are not seen much and few old timers know about them ( I am a old timer so I can say that) . They are in the warehouse and I am dissembling one of them. For the age it is in vary good condition over all. The things is about 150 pounds or more and is 5'+ long so to move it around you would need 2 people . Just an update
That's what I can recall, hope it helps.