I have frame 12470, and BJ confirmed that it's a 1977. They won't look up or print the shop card anymore, like they used to. My frame has no braze-ons at all for cables, excepting the stop for RD housing on R chain stay. Are you sure about the 2nd number of the serial -- doesn't look like a 2 in your photo to me, but I can't see it that well.