Here are a pair of Zenith I have in the collection. One from WW1 and one from 1931 ones like it's little brother the other the big brother and all most identical movements.
The Zenith US Army Signal Corps wristlet and Zenith Special from 1931
The movement from the Zenith Signal Corps wristlet
The movement from the Zenith Special the two sure look alike.
Wrist shots of the two.