Great find!
Wow, even in the 70's I would think they could come up with a better solution to powering Vader's belt/chest lights than that! Smaller battery types were available, even back then. I'd bet that monstrosity gave Dave Prowse a sore butt at the end of a long days shooting. Now we know why Vader never sat down much in the movie. ;)
I have a couple B&W stills from the cell block and trash compactor scenes that are pretty similar to those other shots. Found them at a bottom of a box of unrelated movie photos at a swapmeet in the late 80's, along with a candid shot of Mark Hamill and Peter Mayhew in costume on the Muppet Show set. I've never seen the Muppet one printed anywhere.