The book I have is Langs. To Stop Time, which has the 1954 info; here is the extract.

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" 341 Heuer, Carrera 3147, ca. 1954.
Waterproof screwed steel case with dual function buttons. Black dial with 45 - minute register, date aperture by the 9, and luminous hands.
Movement: Landeron Caliber 189, 13.75 lignes in version 2. Balance with flat hairspring and Incabloc shock-resistance. Diameter 36mm.
Special feature: first chronograph with date disc."

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62/63/64 seems late for first chrono with date disc? Yes - No?

The book I don't have is 'Mastering Time'. (is that a TAG book?)

Would it be fair to say that Heuer or more likely TAG are quite good at presenting Heuers' efforts in a more TAG corporately convenient fashion?

I don't know but as I said, Lang's book is pretty accurate with everything else and mid 50's seems right for first date disc and the Landeron movement is also a 50's thing.???

Regards

Alistair