Thanks
It is not straight sided spline
My first calculations was exactly as your assumptions , but the depth of the teeth was 1.15 module not (one)module [.45module add & .55 module dd]
I have a spline out of all the standard
external spline
number of teeth 30
outer dia.(major dia) 31.7 mm
inner dia.(minor dia) 29.4 mm
this make the tooth hieght larger than one module
according to the ISO major dia should be 30 OR 29.9 mm
I cann't find the proper classification...