I thought there were no "formal" Service Manuals until the 70's era. Not sure which year but since I have owned a copy of the '74 and '75 and '77 Service manuals, I guess that the rumor is that either '70,'71,'72,'73, or '74 was the first year.
As for "formal" Owners Manuals I don't know, but it would sure be good to establish the facts for once and for all.
The packets of assorted paperworks in a manilla envelope prior to the first "formal" manuals is another story altogether, I do not consider those to be either Service nor Owners manuals per se.
____ d'drummer ____