the rear cluster...unless there's something about an "early" SC that I'm unaware of, that shown in the OP is not typical of Cinelli, this is:
And this is what a '70s BB shell and serial number looks like, too (pics from WoolJersey)
The OP's bike is different in both details but clearly not a typical Windsor Pro, either. Sounds like an Italian BB shell and not a Columbus steering column....hmmm...and the Cinelli SC would have a 26.2 seat post, not a 27.2