Soligor coined the "C/D" tag as an indication that this lens was part of their top-of-the-line lens brand.
The "C/D" stands for Computer Designed.
Vivitar had their "Series I", Tamron had their "SP", Tokina had their "AT-X"...all were top-of-the-line lenses.
The "C/D" had nothing to do with "catadioptric", as many other Soligor lenses were also called "C/D".
The "T-Mount" was a universal mount invented by Tamron in the late 1950's.
Originally, the T-mount was strictly manual...no coupling of any sort between the body and lens.
Then in 1962 came the T-2 mount with the same 42mm thread with a slightly different pitch, still completely manual.
After that, all hell broke loose with various ingenious and sometime clumsy ways of attaching universal mount lenses, with diaphragm and/or meter coupling, to SLR bodies: Adapt-All, Adapt-A-Matic, T-4, TX, Adapt-All II, Y-S, etc.
Now, with the use of simple, inexpensive adapters, mirrorless digital bodies are being used with legacy lenses.
The more things change..........