I've seen several grey with pink lettering C-Dales pictured here. IIRC they were all mid to late 1980s road bikes, so they would be SR or R models. Begin looking in the catalogs, and if it were me, I'd start in '86 or '87. Generally, the grade of the components delineated C-Dale models. Better groups gave the particular model higher numbers.
Cannondale Catalogs