M3 - illumination window weirdness

[lefse]

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Hello experts! :-)

 

Anyone here who can tell me what I am looking at in the rangefinder illumination window?

It’s a double stroke Leica M3 from 1957. Works great, and the viewfinder doesn’t show any other problems.

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[105012]

Could it be oxidation? Anyway, will likely result in dimmed frame lines. I would get the M3 serviced, these are amazing cameras and a good service will set you up for many decades of enjoyable picture making.

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[TomB_tx]

The window on the M3 is very lightly etched to frost it on the inside, quite different than later models. It looks like some substance has migrated onto the frosted surface from the edges. Possibly oil from a too vigorous CLA, or perhaps fungus. I expect the M3 used a glass window instead of plastic, so it should be able to be cleaned, which might be a good time to have a full service done. If it can't be cleaned I don't know if M3 style are still available, or if it would have to be changed for a later style.

[lefse]

The window on the M3 is very lightly etched to frost it on the inside, quite different than later models. It looks like some substance has migrated onto the frosted surface from the edges. Possibly oil from a too vigorous CLA, or perhaps fungus. I expect the M3 used a glass window instead of plastic, so it should be able to be cleaned, which might be a good time to have a full service done. If it can't be cleaned I don't know if M3 style are still available, or if it would have to be changed for a later style.

Interesting. I hope it’s not a fungus infection, eating away... but I don’t see what it would feeding off. If it’s only uncoated frosted glass?

Edited October 7, 2018 by lefse

[earleygallery]

Could it be desilvering of an internal mirror I wonder? We need a diagram of the M3 rangefinder assembly...

[earleygallery]

Actually I think it's the dreaded signs of balsm separation of the rangefinder prism - see here http://www.angelfire.com/biz/Leica/page10.html