Remounting Wide Field Ektar to Another Ilex Acme No. 4

I have a 190mm Wide Field Ektar that's already mounted to a mostly working Ilex Acme No. 4. The preview button, "T" and "B" settings are inoperable but the shutter otherwise seems accurate. A local dealer had a very nice No. 4 for a reasonable price, so I bought it, thinking it would be a straightforward swap. However...

The new shutter came with a couple of adapter rings for front and rear elements, and these were easily removed from the new shutter. It now sits ready to have my lens installed

After removing the lens and old shutter from the lens board, I managed to remove the front and rear elements of the lens, and even removed the rear adapter ring quite easily. A test fit shows the rear adapter ring and rear lens element fit the "new" shutter just fine. The problem is with the adapter ring on the old shutter. It's brushed aluminum, and appears to be threaded right in to the shutter. It will not come loose. I've tried sheets of rubber, and even a jar lid remover from Boss unit's kitchen. No luck. I even resorted to gently (and I do mean very gently) tapping around the ring with a jeweler's nylon faced hammer, so as not to damage the concentricity of the ring or the threads. I don't want to resort to anything with jaws, even padded. It it possible that the ring is "cold welded" or otherwise permanently attached?

Any ideas from the group? TIA.

PS - Plans for the old shutter are to go for repairs, and keep it for another lens.

Seized from dissimilar metals and corrosion. Get some penetrating oil and keep the threads wet with the oil for 24 hours then try again.

Being very careful not to get any of the oil on the shutter blades!

I have also found that putting masking tape on such rings helps to get a better grip by a lot more than you might suspect.

Be sure the overall length in the new shutter is the same as the old. Some Kodak lenses had special shutter fittings.

Try heating locally and patiently with a small soldering iron.