First execution screw-back (as shown below) is 38.6 millimeters across the dial (not including crown or pushers);

2446C snap-back case is 40.4 millimeters.

I don't have the second execution screw-back case, but perhaps another reader can measure one of these.

Jeff

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: I'm a vintage watch collector looking to purchase an Autavia 2446 (not, alas, the rare large sundial first model) and I've noticed that these watches are listed as being anywhere from 37mm to 40mm in diameter without the crown. Can anyone please tell me it the case size of this model varied during its production or is this simply a case of sellers giving imprecise measurements?

Personally, I prefer a 38mm watch to a 40mm watch, but I'm also just curious. The reference tables don't mention this.

Thanks, Eric