Late 1970, CSX 2318. Had recently bought a 911S when a friend decided to sell his 289 Cobra for about $5500. At the time I really had no attraction to it because it was not a car you could use as a daily driver, you know to go EVERYWHERE (1 car). Besides, who wants a 2 seat convertable with just a soft top and no A/C when you're chasing skirt in Hot central Calif? Here is a copy of an old Polaroid, it was nice too:
Several months later I passed on a 66 GT350 for $1700. At the time the 911S just rang my bell, should have given up women, I'd be a lot more flush.
There were others, but those are two of the standouts.