Hi Frank,
I'm sorry to read about your M6, and that photo looks grim for sure. However, there a few points that should be made:
1. You have had it 3 years and only put 5 rolls of film through it? The camera should be excercised once a month at least, if not weekly just to prevent mechanical seizures through erosion. The Ms were built to withstand 100 000 to 200 000 actuations and should be serviced if they are not used on a regular basis.
2. Did you take the batteries out of it? If not, then these things sitting around in a humid environment, encased for years will lead to problems. Compared to Germany, NY is extremely humid.
3. Also, if an M6, then this camera could be 20 years old... the M6 TTL up to 9 years old..... no other manufacturer in the world could replace the top plate on a camera of that age, let alone would do so.
You might want to check your serial number vs these:
http://www.cameraquest.com/mtype.htm
and try to date it, then ask on the Leica user forum, or photonet Leica forum... there are many real experts there that may be able to offer some help.
As is, $500 isn't cheap, but your camera will be returned with a full service... and a replacement M6 would cost a good bit more. You will get your camera back as good as new... and nobody else but Leica would do that for a camera model out of production... so despite the cost, I don't think you can reasonably expect Leica to replace any components for free... I mean, you aren't the original purchaser anyway.
Being aggresive well not help you.
Instead, post on the other forums, find out if anyone has seen anything like this, if it is batch dependent or not.. and then maybe you may be in aposition to discuss things further.
However, you aren't the original purchaser, the camera is anything up to 9 years old if the TTL and 20 years old if not... and in a sense you are lucky that the top plate is replaceable at all.
Again, my commiserations, I would be gutted to see that happen to M6, but do some more homework... and take the batteries out when storing for long periods if you haven't already.
Best wishes-
Andy
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http://www.flickr.com/photos/andymclean5/