That looks like a Campag bit of outer from my era :)
https://velobase.com/ViewComponent.aspx?ID=043b3439-c160-4c31-bd1d-1d986376c2f3
Blimey they were shockingly expensive BITD. Yep, just cut off the ferrule from the outer....
Don't know much about colnago so had a bit of a read here about the Arabesque
https://ciclicorsa.com/news/colnago-arabesque-a-steel-jewel-with-precious-details/
Will a ferrule on the outer help? Seem to remember the official campag one that was just silver exposed metal had a ferrule that fitted into the chainstay stop.
I worked in a bike shop back in the 70's and must have changed hundreds of "blocks and chains"
Bolting on a hardened steel tool against a cheese like metal made the metal of the slot peel sideways like a banana skin.
Often easier to remove the cogs and stick the body in a vice.
I bought a watch from the states and also got a tax bill which was a bit unexpected.
I ignored several letters until one came from a debt collection agency......
Thanks for the info :). I've got a Paramount frame...... Ultra short wheelbase, drilled lugs and dropouts, shot in stays and almost straight forks. Sort of has Pongo written all over it.