Open Mike-
According to Mike Longwell's book on the history of CFM, there were only 101 D-35 slotheads made in 1968.
227 were made in Ebbie's year of '71, and only 674 others between the years 1966 and 1973. Compared to the 22,284 D-35s made in those same years, it would seem you have a pretty rare commodity on (in) your hands.
When I win the lottery jackpot, I'll be looking for one of the D-45SS 12 fret slotheads Steven Stills designed for Martin (somehow though I still don't think I'll sound like him).