They first appeared maybe '71, but definitely by '72, usually paired with the solid state Concert Bass head; a suggested option in the '72 catalog was to match it with the 190B, which was the final variation of the 200s head.
Actually 1972 was the first "Hartzell" model line up. Some of the notable changes for that watershed year were the crowning of the transistor as king and subsequent elimination of all
tube amplifiers except for one guitar and one bass designated two 6550 output amp, and one guitar and one bass designated four 6550 output amps, all SS rectified and under the nomenclature "190" and "350" series.
Of course this wasn't a "Sunn specific" trend; this transistor takeover was widespread across the MI industry as a whole.
Also for this lineup the rear loaded speaker cabs gave way to the front loaded cabs, JBL became a custom order item rather than OEM, and the biggie...
For the first time you could order Sunn amplifiers and speaker cabs "ala carte".
As most of us here are aware, prior to this era you could only buy an amp paired with one or two of its specifically designated speaker cabs; e. g., a "200S" wasn't an amp, nor was it a cabinet, it was the amp and cab
together. In 1972 you could order any amp or any cabinet solo, or combined with any other amp/cab.
So, if in fact the 215S/M/V was "usually paired with the solid state Concert Bass head", that really just means that the transistor Concert Bass head outsold the other Sunn amps available on the market.