Cooke Series II 12.75" Anastigmat - Disassembly, Stuck Focus Ring

Not much information on the internet - a little, but not enough, so I thought I'd ask here.
I have a Cooke knuckler, a 12.75" f/4.5 Series II lens, looks exactly like this one (minus the shine):

Attachment 208655 Attachment 208656

The soft-focus ring, actuated by using the "knuckles" is stuck. But really stuck.
I need some more leverage, and in order to get that, the middle element needs to be removed so that I don't damage it.
I just don't know how.

Online reports say this element is cemented in there for good. Others say it's cemented but can be removed by soaking in the right solvents.

Does anyone know how to remove the middle element?

Thanks in advance.

Old lubes can turn tar-like... Sometimes a stuck ring etc can be freed by a repeat application of lighter fluid, alcohol, acetone, silicone spray (containing acetone) applied with a hypo syringe in microdrops, then waiting awhile before another micro application, but you have to survey what is around that area that can be affected by the solvents (paints, iris blade materials, lens cements etc)... Maybe a little heat from a hair dryer to warm parts etc...

But the process depends on what's needed in your case, so be wise or send it out to an expert...

Steve K

Thanks, Steve. I have an expert looking at it right now, so it's safely out of my hands.
The middle lens removal had me stumped when I tried, and I wanted to know if anyone succeeded in removing it, and then putting it back successfully.

All information needed is already posted here!

For example : https://www.largeformatphotography.i...issing-a-screw


Or

https://www.largeformatphotography.i...es-repair-info

Thank you, Steven. Very helpful.

Has anyone successfully removed the middle element, if so, how was it done?