Braze-ons, use of allen head bolt and plastic cable guide under the bottom bracket also say at least 80's or later to me. Fork looks 90's as does the headset - earlier forks usually have a crown and the curve is closer to the bottom. Cast drop-outs suggest it's at least a mid-range frame as a bottom end one would have flat pressed drop-outs and a pressed rear brake bridge. Same goes for the cable routing which you would not find on a low-end frame. If you can measure the diameter of the set post it will tell us something about the grade of steel. 25.4mm is normal grade steel, 26.0 is something like Reynolds 501, 27.0 - 27.2 will be Reynolds 531 or similar.