Over the last couple of years I’ve been buying a few View-Master items as time permits. I have one of the old Bakelite types from the 50’s to 60’s and another of the red, white, and blue from the 60’s. The older model E was somewhat grimy so I finally summoned enough courage to disassemble and clean it. While I didn’t find instructions for the older model they apparently hadn’t changed overall mechanical design and the instructions for the later models (http://www.retrofixes.com/2013/07/vintage-view-master-1962.html) worked pretty much the same. I used an alcohol to clean the windows and eye pieces and you’d be surprised how much crud came off on the q-tips. The difference isn’t really too noticeable on some discs but is hugely noticeable on others, depending mainly on colors and depth. As always, YMMV. Also, if you have one that needs cleaning but you’re nervous about doing it yourself, leave a comment and I’ll get in touch.
As an addendum, tonight I also cleaned the newer model. It came apart in much the same way. If you are working to open these up to clean them, I recommend separating about 1/16″ maximum at each of 4 corners until the spring-loaded keepers are finally released. Going too far at once will most likely weaken or permanently damage them or the bakelite/plastic, where a little patience would have served much better. Also, use a plastic pry tool; I’ve been using a screwdriver but obviously plastic won’t deform the bodies and would be about 1000% better.