I have been told by all the experts that they all had serial numbers, yet I have a similar example. The watch is pretty minty and shows little if any signs of polishing or wear...yet there is no serial engraved between the lugs. Not even the faintest signs of a serial number, so I tend to agree that some examples were shipped like this.

The seller told me that the watch was a sample from a Heuer salesman...while I doubt there is any truth to that story I can't see how the serial just disappeared from a very strong case.

: Hi gents,

: Trying to solve a bit of a mystery - have picked up a 7763 that has
: no trace of a serial number. The case does not seem to have been
: heavily polished (or even at all). Correct movement, black and
: white two-register, matchstick hands, appropriate location and
: type of wear for its age - all seems legit. I'd like to think it
: is a prototype or –? Anyone have any ideas?

: Thanks and happy collecting,

: Dan