Yes, we see this a fair bit, where a nickel-plated bridge apparently for a Cal 11 has had the model reference machined out and 12 stamped in the resulting pit.

There are a few possible theories about this : http://www.chronocentric.com/forums/heuer/index.cgi?page=1;md=read;id=30316

I tend to favour Heuer not expecting to have to replace the Cal 11 so having bridges in stock and reusing them as Cal 12 bridges rather than junking the lot. Interestingly, we sometimes see late production watches around the tail end of the 70s with this nickel-plated bridge so the stock must have been quite large - it just makes business sense to use it up than see it remaindered and we see this pragmatism sometimes with other parts as well.