Originally Posted by T-Mar

That's what I'm leaning towards too, at least for the cable tunnels. The long dropouts pretty much disappeared from use after 1977, when the short, Portacatena dropout was released. The eyelet-free dropouts first appeared in the 1974 catalogue. So, 1974-1977 seems the most probable date range. They definitely had brazed-on bottle and lever bosses by then but the cable tunnels were pretty rare.