From what we see in the wild, it's clear that Heuer had worked with their case manufacturers to allocate specific ranges to each of the Chronomatic watches. They don't run together at all, there is clear and distinct separation between Autavia (141xxx), Carrera (147xxx) and Monaco (157xxx).

So much separation in fact that when we sequence by serial number we see the models running in specific ranges for some time, so Heuer was obviously allocating a wide space for each of these watches. Other contemporary watches like the late Camaros and second and third economy watches have higher serials, so it's no stretch to assume that Heuer had been ring-fencing these blocks of serials for some time ahead of the launch of the Chronomatic watches. It also means we get some dating anomalies for a whole chunk of serials between those lowest s/n Autavias right up into the mid-160xxxs.

Given that it appears to have been planned for some time, I see no reason why a decently sized block of serials wouldn't have been allocated for the initial run of Autavias. I have no problems with a 1413xx watch being from that run. Heuer was taking a bit of a punt on Monaco sales and later evidence seems to show that they overestimated volumes on that watch, but they would have had a much firmer idea of how many Autavias they would be likely to sell, with 6+ years of sales figures to go on. The 1415xx is undoubtedly an outlier but we have seen on plenty of other occasions that Heuer were not afraid to mix and match until parts supplies were exhausted.

We have seen xxx1xx watches in both the Autavia and Monaco Chronomatics and I have seen nothing to suggest that the xxx000 serials in their respective ranges weren't allocated to watches. As we haven't seen any surface though, I wonder whether a lot of these were for prototypes and perhaps even while they were still finalising case design while the final dimensions of the (modular) movement were still being ironed out too. It makes a lot of sense to me, but I'm only speculating. Oddly enough, the few Carrera Chronomatics we have seen have been higher in its 147xxx serial range, so something different seems to be going on with that model. I'm at a bit of a loss to understand why, I see no obvious reason why there are so few Carreras compared to the other two - Heuer were aware of the volume of manual Carreras they had sold compared to Autavias, but that isn't reflected in the number of Carreras we see. The late first generation Carreras were also still selling strongly at this point, but that doesn't seem to be a good reason to throttle supply of Chronomatics. My best guess would be that, with the Cal 11 partners struggling to ramp up supply of ebauches quickly enough to meet demand, Heuer allocated most of the movements to the more expensive watches. There was hardly a night and day difference between the Carrera and Autavia price though, and margins on the Monaco were probably squeezed a bit as they were more costly to assemble, though they did have novelty value to help them along too. If it was only the movements, we might expect to see more spare Carrera Chronomatic dials floating about too, but they seem no less rare than the assembled watches. One of the enduring mysteries of Heuer collecting then.

So quite a long post to say I don't see a problem with Rich's and TH museum's Autavias having 1413xx serials!