Mottled front element - Braun Katagon 50 2.8 - Staeble Werk

[Braddanman]

Here is a Braun Paxette bought yesterday at auction including the above lens.

I CLA'd the lens this morning but I cant rid it of the mottling on the outside of the front element.
I've used cold cream, lighter fluid etc but to no avail.
Is this coating damage?
The quality of this lens isn't that great and I'm not sure that cleaning this further will make that much of a difference. However if it will can somebody recommend something that I could polish the element with to to remove the coating entirely.

Included was the Roeschlein Kreuznach 135 5.6 in excellent condition. Just a bit stiff to focus so only need to relube the helicoid.

Min focus of the 50mm is just under a metre. Using a 39/42 ring and an M42 adapter this is reduced to about 70cm due to the longer registration of the adapter, infinity with the adapter is only about a couple of metres. As this is the cheapest M42 adapter and it doesn't have a face plate I'll have somebody turn the adapter to 44mm in length so I can use them both properly.


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[guardian]

Wow, tough one!!

Polishing of lenses without impacting their optical characteristics is above my pay grade! I don't know how to accomplish it.

Only approach I know to removal of coating is through use of hydrofluoric acid. That's also above my pay grade, I'm afraid. Hydrofluoric acid is really dangerous, powerful, stuff.

[Braddanman]

I was not thinking of going overboard with it. I feel that just using a lens cloth with something like T-Cut (a paint restorer) or something like Brasso?? a very liquid metal polish might just be enough but would like somebody's experience before proceeding.
I'm assuming that it is actually coated. It seems to have a slight blue tinge when shining a light through it.