There a section of exposed metal around the bottom bracket. It is shiny. Could that be chrome?
The frame got some love with 8 speed upgraded drive train, rx100 Shimano sti, and is cold set to 130mm.
Between the paint and drive train upgrade a lot of effort was invested. They wouldn't have gone to such effort for a low end frame, would they?
Closest match is this frame:
http://simplicityvintagecycles.com/2...-rejuvination/
But could the 5 in the s/n be for 1975?
This would mean the cable guides and dt shifter braze ons were added at the time of the repaint!