well assuming it's repainted there are a few non-paint clues: the shorter rear dropouts are late '70s at the earliest, the brakes are external-nutted; there doesn't seem to be any brazed-on shifter bosses (any remnants?); one pair of water bottle bosses I can see; the lugs are long pointed and have window cut-outs; under BB cable routing and top-tube cable tunnels. All pretty consistent with a frame from the late "70s to early '80s. That's my best guesswork