In most cases, the iris scale stays witn the barrel, so you would unscrew the top section to remove. I'm viewing this on my phone, and the way i see it, it looks like yours is all one piece.
It may not be designed to be removable. My Agfa Super Intergon is like this. If the flange can be unscrewed, maybe you could get a machinist to mill an adapter for you to "front mount" the lens in a larger shutter.
Thanks for the response Chris. It appears to be one piece. I am glad I only spent 7€ in the shutter which works beautifully. I was under the impression all Heliars and Xenars in 210mm could be fitted to a Compound 3.
I am using the Heliar with a Speed Graphic so there's no need for machinery.
I'll hold on to the shutter until some interesting cells come along. Now the ƒstop scale is pretty funky, it appears to be in milimeters (2,6 - 5 - 9 - 13 - 17 - 21 - 25 - 29 - 33 - 37 - 41)
With some exceptions, most Voigtlander LF lenses cannot be exchanged between barrel and shutter. As you've seen, the mounts are different. Also the spacers on the shutters can be custom for a specific lens, so sometimes swapping one shutter for another wont work either.