Looking for DIN specs--911 steering wheel hub splines

[Jameel]

I'm looking for the DIN specs for the internal splines found on 911 steering wheels and hubs from 65-89. I'm aware that the steering wheels changed form in '74, but the splines themselves remained the same. I need to have a broach manufactured, but am having a hard time finding actual DIN specs to supply the manufacturer, aside from the basic dia. and spline count. Thanks.