Hi Richard. What you describe is a slightly undersize 26.4 bar made for a standard Cinelli 26.4mm stem. I've sometimes managed to fit a Cinelli 26.4mm bar in a 26.0 Nitto or TTT stem w/ careful prying and a bit of lube. You might want to check your caliper against a tape for accuracy. Cheers. Billy Ketchum; Chicago, IL; USA.
I have Cinelli drop bars measuring 26.2-ish at the clamp. No, not obviously crushed. Bars are in excellent condition. Is this the bar Cinelli said is 26.0 ? I don't want to damage the wrong size stem.
Mod. 64 stamped; "Giro d'Italia" surrounded by palmeres; helmet & shield "Milano" logo. Clamp area is knurled left-right. Sleeved center section. Polished alloy. No aero routing gooves.
I have no idea of date of production though not 60's. 70's - 80's maybe?
Chicago, Illinois; U.S.A.