It seems to me that manufacturers weren't as fussy about box X belonging with watch Y as they are now. Heuer seemed to use whatever was to hand when sending the watch out, and any confusion that caused was added to by the retailer doing the same.

Given that, and the box stating automatic, it's fair to say it doesn't belong to either watch as such. Which isn't to say that the watch wasn't supplied in that, for the reasons above. Time-wise, a second execution 2447 could have been a contemporary of the automatics, whereas a Dato would have had to have been hanging around years longer to end up in the same box.

Heuer boxes have a value of their own now, so for the best return you could try selling it separately. Keeping it together, then I would probably plump for the 2447 as the more contemporary and more valuable watch.