These lens were manufactured by tokina and mainly sold by Soligor (allimatsu corp)
This was the soligor reply to Vivitar series 1 (all were 1974-1976 productions)
C/D means (an ONLY means) Compact Design because these lens were as big as previous productions but 1 stop more opened (usually f2 instead of 2.8)
The first production line included 28/2 + 35/2 + 50/2.8 macro + 135/2 + 135/2.8 + 70/220 3.5
Quality is usualy ok (not georgous but ok) .. Later, Soligor sold also c/d lens manufactured mainly by sun (ogino) (28/80 .. ) but the quality was mixed