The mod 49 was introduced in 1949 and I think remained the top model until 1957, when the mod 57 came out. However, like many French manufacturers, Stronglight kept making older models, simply pushing them down to cheaper bikes. From the headbadge, your bike sounds like late 70's, so the mod 49 could have been original, pretty sure this model was made into the 80's. One consequence of this practice is that you will see Stronglight mod 104 and 99 with old Stronglight extractor thread from the days when they were top models, but also examples with Campy-compatible thread from the 80's when they had become mid-priced cranks.
> I took another look, and I'm pretty sure the tubing sticker once said
> "1020". Which places it in the 1974-1977 time frame. But *none* of the
> components are correct! I suspect someone transfered the parts from an
> older bike to this one. There's a dealer sticker from Gamache's
> (Fitchburg) at the base of the seat tube, so it was probably a complete
> bike as sold (rather than a replacement frame to which someone transfered
> a batch of parts from a busted frame).
> More details: I can't find a model name, but it's blue with some black
> panels on the seat tube, chrome fork crown and the bottom half of the
> fork legs (no chrome on the stays though). Gold lettering "Motobecane" on
> the downtube and some gold striping here and there. The headbadge is
> clear plastic over a printed plate, fastened by two rivets (top and
> bottom). 27" wheels with alloy rims. If there are markings on the rims I
> can't see them. The saddle is a dreadful-looking plastic thing, on a
> straight alloy post (with a shim - more non-original?).
> By the way, the Mafac Racers may not be original, but it had centerpulls
> - the rear brake mounts to the intermediate stays, with brazed on cable
> guides and all.
> How long was the Stronglight 49D in production? By the '70s the 93 was
> top-of-line, and before that there was the 57... I would expect the 49D
> was old when it went on this bike.
> Looks like I have a cache of interesting parts.
> By the way, anybody familiar with the brake levers as described? That
> J-shaped slot looks kind of untrustworthy.
> Thanks for all the info!
> Karl Frantz
> Sterling, Massachusetts