Caveat: I have one with a G4F8 (June '78) serial number, that I bought locally from the original owner. Campy dropouts.
And a dove stamp on the steerer.
Some TX770's were indeed stamped as TX700s. Check your steerer carefully. Your 531 sticker probably sews it up, but still...
One of these days I need to strip it down to bare frame and weigh it vs. my same-size '78 TX700 frame, using the same scale at the same time. Previous bare-frame measurement (no cups or head badge) of the TX700 frame was 1.97 lbs.
