thruout the 70's and 80's ,Bertin bikes were all of mid-level and higher quality bikes. AFAIK, there were no slap-em-out bike boom equivalents to, say, the ubiquitous Peugeot UO8's etc. . Tubing materials will range from various straight guage Durifort and Vitus ChromeMolys on up to butted lightweight Reynolds 531 SuperLegger and 531C. Models to look for include the C32, C34, C35, C37, C70 , etc. but identification is difficult as there will not be any outward obvious decalling or markings to indicate the models. Mostly you can look at the lugwork, tubing used, detailing and associated components to judge what general level of bike it is.From there I'd just suggest that you go with your instincts of what will be required for repair or restoration as they can be very , very french.