Unfortunately without a case I found this high quality movement in the canadian bay:
The size is 38,96 mm on the movement side and it is build flat with 3,28 mm. Here is another detail photo of balance and escapement showing the beautiful refinement:
Except the missing of the cross geneve the dial side is a eye candy:
Even the cover of the wheels has a light stripe finish.Especially nice the intervention for the fine adjustment of the two-piece lever:
THe only additional information I've is a presumable age 1925-1935 depending on the style of the dial :
Funny is Zenith produce those days a flat caliber, the E.P.V.S. , with in a simular flat size. I can only assume that in relation to the demand there was a production bottleneck or that these movements had been a bargain. I do not have the slightest idea who built this beautiful ovements. Any hints are welcome.