We see many anomalies in the world of vintage chronographs, and so too with the vintage Heuers.

That said, the highest serial number that I have for a Reference 1163 "Siffert" is in the 242xxx / 243xxx range, and every Reference 1163 Autavia in the 339xxx range has a black dial. In summary, this case was produced long after the last of the "Sifferts".

If you like the watch, then try to enjoy it. But most collectors who are in the know would conclude that it has been re-cased and apply a significant discount, in assessing this watch.

Jeff

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: Likely from c1976 - see article by Mark Moss;

:
: http://thoughts.onthedash.com/thoughts/serial-numbers-of-viceroy-autavias/