The cases were created in batches, typically of thousands for the biggest "series" watches (Autavia, Carrera, Monaco) and of hundreds for some of the less popular models.

A contemporary Autavia and Monaco, say, could still be separated by several 000s of serials, especially if a Carrera batch came in between.

What happened when the Chronomatic watches were launched is that Heuer anticipated big demand (which, if you read Jeff's piece on the Viceroy Autavia, didn't necessarily materialise immediately) and assigned large ranges of serials ready for these watches. What they did do, however, was also include manual cases in the same batch ranges, above the equivalent automatic case range.

You end up with something like this:

Autavia 1163 141xxx - 144xxx
2446 144xxx - 146xxx
Carrera 1153 147xxx - 150xxx
73353 151xxx - 152xxx
73453 153xxx - 154xxx
73653 155xxx - 156xxx
Monaco 1133 157xxx - 163xxx
73633 164xxx - 166xxx

Those ranges are rough and ready, but are a reasonable guideline. We occasionally see a different model "intruding" on a range, but as a rule of thumb they work fine. But you can see what I mean about contemporary watches being separated by quite a big range - a 141xxx Autavia could be made at the same time as a 164xxx Monaco, for example.

So we can conclude there were numbers for manual Monacos allocated in the initial range for the launch, so 1969. The 1972 date you refer to is presumably from the OTD MOAT - that's out of date information, presumably from when OTD had fewer catalogues available to research. 164xxx Monaco 73633s, then, will be from 1969/70 rather than the 1972 the MOAT suggests.

We do, however, know that there are some oddities in Monaco numbering, as discussed here:

http://www.chronocentric.com/forums/heuer/index.cgi?page=2;md=read;id=55380

These are 1533s in 1133 cases that date from before the movement was available, but that Abel (and others) have confirmed are original. So Heuer was clearly not above using Monaco cases at anachronostic times for purposes for which they were not originally intended. Perhaps we should take any attempt at dating a Monaco with a healthy multi-year margin for error then!