I think you've got it all figured out on when the different Cinelli bars came out! Chuck is the man on dating of the stuff. I would've hoped Columbus would have taken better care of the company, now they've merged with 3ttt which was OK in the 70's also...
I too hunted high and low for NOS Old-Logo 66-42's and was unwilling to spend the $300 as one retailer wanted... I finally "scored" after a year of watching E-Bay and asking around a lot... I haven't seen any lately and I watch all sources. Good luck on your search, it's well worth the wait! My 64-40's are now just a shelf piece, the 66-42's are the only way to ride!
Regards, Bruce Van Remortel, the AF Guy presently on Guam, 78-88 degrees everyday...