Image plane mark on Grass Valley Infinity

Question

I'm working on a Grass Valley Infinity and for a specific application I need to know the image plane position (ie sensor position).

But I can't find the image plane mark like this :

So I have two question :

1. Is someone know any informations about this on the Grass Valley Infinity ?
2. Is there always an image plane mark on a camera ? I thought it was a "norm" for professional cameras.