Silent Behind The Scenes Test Footage, featuring proto-type puppets from the 1982 movie, sourced directly from Joe Tripician, who worked on the movie.
There is no audio, but it features many interesting puppets! Namely the second and third proto-type skeksis, Mongra and Mal, as photographed by John E. Barrett, a photographer who has worked with the Jim Henson Company throughout the years.
In Jim's Red Book, notes from Joe Tripician were published
I've posted the video on Internet Archive, along with Barrett's photographs, in an effort to preserve them for future fans!
Video sourced from https://www.youtube.com/watch?v=UbTyfSne_u0 Joe Tripician. Photographs...
If all this interests you, check out the Jim Henson Company's published test footage from around the same time, possibly the exact same test!
https://www.darkcrystal.com/galleries/dark-crystal-galleries/behind-the-scenes-test-footage-clip-1/
https://www.darkcrystal.com/galleries/dark-crystal-galleries/behind-the-scenes-test-footage-clip-2/