After some additional detective work plus info from several CR members, I've concluded that the mystery frame is a 1981 or 1982 Bertin C79 SSC model made of Reynolds 531SL tubing.
It has a boss for Shimano aero shift levers brazed on the top of the down tube plus 531SL style wheel clearance flats in the chainstays.
http://www.flickr.com/
According to information provided by a CR member, Reynolds introduced 531P (Professional) tubing in 1981 (maybe 1980). It was 531SL 5/10 tubing upgraded with Reynolds 753 chainstays. By that time they were probably 753R stays.
I have two OT Reynolds 753R bikes, a 1984-85 Holdsworth and a 1988 Peugeot Chorus. They both have round-oval-round chain stays as does an OT late 80s Gazelle AB made with 531C (Competition) tubing.
As far as I know the flat wheel reliefs where only used in 531SL chainstays. All other Reynolds 531 chainstays that I've seen were round, crimped or round-oval-round.
Bertin was the French importer and distributor for Shimano. In 1981 Shimano introduced their short lived Dura-Ace AX and 600 AX aerodynamic gruppos. Being the importer, Bertin probably had early access to these components.
The bike has metric diameter tubing. Metric 531SL was quite possibly still in the system (Reynolds' or Bertin's)until as late as 1982.
The C79 SSC model was available as a bare frames or a built up bike (probably Dura-Ace AX). Same thing with the identical C80 SSC model made of Columbus SL tubing.
Thanks for the help solving the puzzle.
Chas. Colerich Oakland, CA USA
D Gordon wrote:
> Hello, I have an early Trek 760 frame with original paint and decals and it
> was built with 531 P (professional) tubing. I know for a fact that all of
> the trek 760s did not use that tubing. Most had 531. Mine was special from
> the factory. If you want pics I can get some if you really want to see the
> tubing or how it was built.
>
> Regards,
>
> -Dee Gordon
> Los Angeles, CA
>
> -----Original Message-----
> Sent: Monday, January 25, 2010 2:54 AM
> Subject: [CR] Reynolds 531SL and 531P revisited
>
> I checked the archives and the internet and couldn't find any answers to
> my questions.
>
> Reynolds made light gage 531 tubing for many years. In the mid 70s they
> introduced a boxed set of 531SL light gage tubes.
>
> Besides the light weight the 2 distinguishing features of these tube
> sets were:
>
> 1. The fork blades were the then new Continental Oval shape similar
> Columbus but different dimensions.
>
> 2. The chainstays had about 3" long shallow flats pressed in for wheel
> clearance rather the the crimps used on most standard chainstay from
> those days.
>
> It looks like Reynolds 531P or Professional tubing was introduced around
> 1980. It was supposed to be the same as 531SL except for 0.1mm thicker
> chainstays.
>
> I'd never seen a 531P frame up close until now???
>
> Questions:
>
> 1. Did the 531P chainstays have the same wheel clearance flats as 521SL?
>
> 2. Was there any overlap in availability between 531SL and 531P?
>
>
> I've recently identified a frame I've had for several years. It has
> Andre Bertin decals but a partial rattle can respray with maybe the
> original white color left as bands on the seat and down tube. It looks
> like whoever painted it also replaced the decals.
>
> I figured out that it's about a 1983 Andre Bertin C79 frame with Shimano
> vertical rear dropouts and a boss for aero shift levers brazed on the
> top of the down tube.
>
> It may have come with a Shimano Dura-Ace AX or 600 AX aero gruppo
> especially since Bertin was the importer/distributor for France.
>
> The frame looks identical to the C80 model in the Bertin section of the
> CR website except for the paint and shift lever boss.
>
> http://www.classicrendezvous.com/
>
> I now own this frame too... :-)
>
> Chas. Colerich
> Oakland, CA USA