Microprojectors and screens
These remnants of the past are not commercially viable products any more. None of the major manufacturers make a microprojector any more. While a lot of manufacturers list screens in there literature they are seldom, if ever, sold.
A microprojector is a system that uses an environment arc or other high output lamp to project the microscope's image several feet away. While this sounds like a great idea the problems are many. The main one is that so much light is needed that it cooks the slide. Even with the best heat absorbing filters a microprojector can fry a specimen.
Most microprojectors will de-colorize or punch a hole through a specimen in a very few minutes. You can watch the specimen bubble and loose color. If this is a very important and rare specimen I would not use it on a microprojector.
However microprojectors give a very good image. The Zeiss Revolver Microprojector was the pick of the litter. Since microprojectors are no longer made if you have one and like it take very good care of it. Make sure your repair tech. can handle it because you can't get a new one.
Screen seem like a good idea but mostly they aren't. A screen is a system that connects to a camera port that projects the image on to a piece of ground glass. This lets you see the image projected.
Sounds real neat but there are problems. The systems need a lot of light, the ground glass makes the image look sparkly or refractile and you can only see the image if you look directly at the ground glass, viewing even a few degrees of center is difficult. To get around the refractile image problem most makers make screen that constantly move the ground glass. This works but the noise of the motor will drive you crazy.
The image on motor drive screens is actually quite good. But they are not used commercially a lot. The noise and the limited viewing angle make these very difficult to use. They are also expensive enough that a color tv. system looks very cost effective.
Ground glass systems built into large research metalographs are part of the reason that the microscope is purchased. But even here tv. is making inroads. Usually the screen is used to show a small number of users the image. Since these microscopes are optimized for the screens they tend to work better.
What this means
Screens and microprojectors are commercially dead. If you have and like a microprojector maintain it, well, you can't get a new one.