The OP and myself have been discussing this bicycle at some length after he contacted me via PM about a week ago. Even before he reported back on date codes, I thought it was a 1976 model.
A 1978 would have a Takagi Tourney crankset and SunTour SL front derailleur, as opposed to an SR Apex and SunTour Compe V. More importantly, the 1978 model moved to the distinctive Huret rear dropout with the integral cable stop, while the subject bicycle has a traditional chainstay mounted cable stop. It would also be rare to have 1976 components on a 1978 model.
Given 1976 date codes, a 1976 or 1977 model is most likely. The only catalogue spec differences between the 1976 and 1977 models are the crankset and handlebar stem. The 1976 uses an SR Apex crankset like the OP's bicycle but the stem is listed as being a Pivo. The 1977 model uses a Takagi Tourney crankset but the stem is SR, like the OP's bicycle. Based on other extant samples and road tests, we know that 1977 production did use the Takagi crankset spec'd in the catalogue, so the subject bicycle would appear to be a 1976 model based on the SR Apex crankset.
As for the frame style, the mixte frame with the wishbone upper tube was available for this model in 1976 and it is listed as "mixte special" in the catalogue.
With the exception of the stem, which could have been a spec change after the catalogue was issued, the subject bicycle is consistent with a 1976 model. So far, all the reported component date codes are from the first half of 1976, so it was probably built in the summer, just before the transition to the 1977 models. If this were my bicycle, I'd have no hesitation calling it a 1976 model.
Last edited by T-Mar; 01-17-18 at 11:44 AM.
Reason: typos and syntax errors