I'd place this circa 1974-1978 and higher end, based on the combination of long forged dropouts without eyelets, cable routing under the BB shell, top tube cable clips, exposed brake nuts, brazed-on bottle bosses and brazed-on lever bosses. Appears to have been designed for a 700C/tubular wheelset. However, it does appear to be a repaint, so it may have been modified. Still, the low rake fork and geometry suggests a 1970s racing frame.

It looks like it says 531 on the fabricated seat tube decal, though whether that reflects the actual tubeset is anybody's guess.