I'll risk a few guesses without benefit of photos (like tightrope walking without a net). Based on the early Shimano components, it *could* be as late as '78, but I'd guess earlier...maybe '72-'75. The wheels with wingnuts might be earlier-era replacements, but I remember seeing some of my first-seen mixte bike from the Benelux countries that used these instead of QRs on what was then a low-cost bike. I thought it kind of odd, but my sister bought a new Gitane mixte around '74 that came with wingnut hubs, so the French were doing it too.