Regarding to your model number question: at the time of the 146 HP movement, Zenith wasn't really consistent in model number designations as far as I know.
This would be the gold version of the A273, so G273 if you'd like, although I have never seen that designation being used. (Or the 3 register version of the G171, therefore G173, which I have seen used once on a very similar - but not identical - watch)
Perhaps someone with the Rössler book can weigh in?