My guess is that it is from the late 60's. I remember selling brown and green Galaxy's in about 1971 and they came with down tube Simplex shifters and black plastic derailleurs. Otherwise, Reynolds 531 frame, 3 piece steel cottered crankset, leather saddle, Weinmann center pull's, Weinmann aluminum rims with 2 quick release hubs. Too bad about the really bad condition of the OP bike. If restorable, it is a major project.