First prototypes of this bike were made in 1977 and rode by Rob Shepherd as official pilot achieving the 4th position on his first championship and 10th position at same time by the US rider Marland Wahley.
Also Eddy Lejeune rode his first SSDT in 1980 with the 200 SEELEY, he was 12 position and the Best Newcomer.
Officially dating from 1979, finally I'm not sure about the final production. But, be carefully because there is some "replicas" on the market.
Let me note that this unit (picture on the top) has a wrong exhaust mufler due to the difficult on the finding spares from these rare bikes. The right one was the same as the contemporary RS's mounted (RS200, RS 220 and TL200) wit only one outlet exhaust tube and the RSC engraved logo.