Need identification help

I need a help with this nice clean movement IWC
I know there are a BREVET 31457 and a BREVET 55231 from 1911.
Serien number dated it to years cca 1926-1929.
But what is it as a caliber number, please?

Like as Kaliber 65-19'''H6 or Kaliber 65-19'''H6,5 ??
there are not / missing/ a stem with crown and I want find it.

So big please
What is it for a caliber?
What all caliber from IWC comp. use the same stem for crown.
Where, / who / can help me with buying a stem for this movement.

thank for your help

Peter

The Date Your IWC app gives the following using the movement #
only.

sorry, I think the serien number is 873 605 and it is a biger format as 12, 5
lig

Hi Peter

From documents I have - Cal 74 will require a StemW1477

I hope this helps