Referring back to a post I did a few months ago on the formatting of the reference numbers:

So that makes the four digit reference numbers of the early 70s take the following format:

XXYZ

Where X is the movement (although 11 indicates either 11 or 12, depending on year);

Y is the model range (e.g. 5 is Carrera, 3 is Monaco)

and Z is the case material as per the previous post.

The suffix letter(s) indicate the dial colour(s).

Ok, maybe we all knew that anyway, but it doesn't hurt to spell it out, right? :)

So an 1133 G is a steel-cased Monaco with a grey dial and Cal 11 or 12 movement, while an 1158 CHN is a solid gold Carrera with champagne dial and black registers, also with Cal 11 or 12.

The only difference for the manual winds is that the reference is XXXYZ.

Y and Z refer to the same things as above (model range and case material respectively), but rather than XX referring to the whole movement number (Calibre 11/12 or 15) the XXX references the last three numbers of the movement. I.e.:

Valjoux 7733: Model ref begins 733
Valjoux 7734: Model ref begins 734
Valjoux 7736: Model ref begins 736

So, to deconstruct the 73633 model reference:

73633 means the watch uses a Valjoux 7736
73633 means it is a Monaco
73633 means the case is steel

Thus we get a steel-cased manual-wind three-register Monaco. Spot on. Got to love it when Heuer have something consistent and predictable, makes the job of the watch archaeologists that much easier!!