Diebel liked big-sounding names. Hence "System 2000" and "Research Grade". Ultima was Celestron. DS was supposed to stand for "Deep Space", but we called them "Diebel Specials".
Meade never made eyepieces, they were always imported. Initially, from Japan. Lately, China.
All the newtonian optics came from Coulter prior to about 1982, after which Meade had it's own optical shop. All the early SCTs were Mizar, and the 4" always was Mizar. The 8" and larger optics were made in-house beginning about 1982.
While I was working there, I had an 826 on loan to take planetary photos with, for possible use in a catalog. I set it up alongside my 8" Optical Craftsmen Discoverer for comparison. The Meade wasn't bad, but the OC was much better. I still have the optics from the OC in my Springfield.
The Research Grade Newtonians were copies of Caves, with a few notable improvements. The castings for the prototypes (in the ad photos) *were* cave castings with Astrola ground off and the thrust surfaces welded on. Particle board was also used.
I have a DS16 mount that I'm planning to put a Byers drive on one of these days for at-home planetary with my home-built 10" f/6 Newtonian (my own optics, made with Dave Groski's help: https://skyandtelesc...e-april-2011-2/ ). I know, it's on a Tak EM-500 in that picture, so why not keep it there? The EM-500 is on a 4' pier at Cosmic Acres now, so the Newt needs a new home.