Does anyone have a bestfit ɓalance staff number for this please?

I am trying to make a wearer out of this 1915 movement and wonder if anyone has a best fit balance staff number please?

Is this an unusual level of decoration for what was probably a trench watch? Also I find the color unusual for an omega?

it seems to be a pretty standard 13 line? And I, for one, am impressed that it still has its inner bezel!