OK, it required removing the stem and the HS locknut, but I had to know. The 1969 Allegro definitely has a 22.2 stem like those Swiss bikes Joe Bender reported. A new Nitto from Rivendell, duly marked 22.2 in case anyone doubted it, slides easily into the steerer. I then removed the HS locknut and looked on the underside. There it was, big as Dallas (as we former Texans are found of saying) - "25 x 1.00 France". Conclusion - this bike has a French HS but a 22.2 steerer. This bike is original all Campy NR including brakes, with old logo Cinelli bars and stem consistent with the frame and the other components. I'd say it's 95% sure these are original bars and stem. I find it inconceivable the steerer was reamed (unless at the factory) as this would have meant someone removed the original 22.0 Cinelli 1A and reamed the steerer just so they could use an otherwise identical 22.2 1A. I would call that totally irrational. Given that we now have an old Allegro (mine), an old Cilo and an old Mondia (both Joe's) that have been confirmed to have 22.2 stems and French HS, I'd say we have a pattern here. It appears the Swiss makers circa 1970 or so commonly used this combination, even though it might not have been a good idea. On the other hand, I've never heard of Swiss bikes having an unusually high rate of broken steerers, so I'm not sure it was even such a bad idea.
Regards,
Jerry Moos, who had to drive to work today in rainy Warren, PA