Cannot unmount front element from Sinar CMV Mount

I picked up a lens in Sinar CMV mount and am trying to remount it to a Copal.

But the front element is stuck in place. A rubber wrench is no help.

Does anyone know if there's glue or some kind of mechanism keeping the front element in place in a CMV mount? Thank you.

Have you tried a radiator hose clamp?

Thanks for replying Jim. Not yet. I've only used a rubber lid gripper. I wrote "rubber wrench" but it's really a lid gripper. A rubber wrench would be stronger I think.

I am willing to try something even stronger like a radiator hose clamp, but I wanted to make sure it's not actually held in place by something else first.

Are you certain there is not a tiny screw to discourage the lens movement?

Thanks Jac. No screws visible from the outside.

I've opened up the shutter and also don't see any screws keeping the front element in place.

Attaching a couple of photos in case they help. Thanks again.

From the first photo you can see there's a black ring behind the front element. I don't suppose that locks the element down?