Many Thanks Mark!
That was of much help. It seems that all my Carreras 12 are quite late , which is a bit disappointing. I much more prefer the very first dials with slim and long hour bars and polygonal caseback... especially now when I saw Jeffs' Carreras :)
... and all three of them are Heuer-Leonidas executions with proper bridges and casebacks, so at least they seem to be all original late 1960s.