Don't know the reason (as in why they are used) but I believe that the numbers represent the shape and style of 'bar. This is from the early 80s.
ie - 66 is called Campione del Mondo and is a flat top road bar with a deep drop
64 is called Giro d'Italia and is a similar shape but with a more shallow drop
I don't have any 'bars with other codes to refer to, there was a Criterium shape favoured by Sean Kelly and other road sprinters which had the tops curved somewhere between a road bar and track sprinters bar. Guessing that there was probably a deep drop, no flat on top track bar as well?
Can anybody add to this?
Matt Memory
Bris-vegas
Australia
>From: Grant McLean <Grant.McLean@SportingLife.ca>
>To: "Classic Rendezvous Mail List (E-mail)"
><classicrendezvous@bikelist.org>
>Subject: Re: [CR]Cinelli years - Handlebars
>Date: Thu, 29 Apr 2004 11:08:44 -0400
>
>List,
>
>Does anyone know the reason for cinelli handlebar model numbers?
>63, 64, 65, 66 ??
>
>If 1963 is the year the aluminum bar was introduced, is it just a
>coincidence that the model numbers start with the same year?
>
>Grant McLean
>Toronto.Ca
>
>
>
>Jan Heine wrote:
>I think that items like a "set of alloy handlebars" as Cinelli's
>first product, presumably in 1944 may be a mistranslation. It could
>be a steel alloy... The same article states 1963 as the introduction
>of the "New Concept" aluminum bars. (This is from Gabe's article in
>the Bicycle Trader.) Or were there other Cinelli aluminum bars before
>the "New Concept" model?