Also, in the '72 catalog under "cabinet nomenclature" they list the cabinet decoding as;
First number = number of speakers
Second number = size of speakers
Letter = type of speaker
"S" = Sunn (transducer?)
"V" = Vega (it seems that Cerwin Vega replaced JBL as the "brand name" driver upgrade)
"M" = Magna (higher power handling than the "S")
It also states in the catalog that "last year" (from this I assume 1971) was the first year you could "mix and match" sound system components, but that 1972 was the first year that you could "mix and match" musical instrument components.