Any clues as to whether a "mystery" frame might be made of 753 vs 531? A local framebuilder (753 certified) said no (seatpost diam, weight, etc). I noticed that 753 seatstays have (mostly?) double tapers. This builder said 531 ss could also be had in double taper. Anyone know or have an 80's 531 frame with double taper seatstays or an 80's 753 frame with single taper seatstays?
Jack Romans
Sacramento, CA