[Leica] M3 RF patch problems: getting better, but...

[geordiepete211 at yahoo.co.uk (Peter Cheyne)]

I posted recently about my newly purchased M3's RF patch being too dim  
to focus.  I'd like to thank those who suggested I return the camera  
to Tony of Popflash to send it for repairs.  It was cleaned the day it  
arrived and swiftly returned.  The difference was day and night!  Now  
it's very bright and great to use.  I took a few photos on a test roll  
of colour negative monochrome then put the camera down.  Easy  
focussing every time.  However, when I picked it up a few hours later,  
I noticed a black spot on the top middle of the RF patch.  It wasn't  
there before.  Even with a gentle tapping on the camera, the black  
spot won't budge.  It takes up a bit more than 1% of the patch, but  
I'm not obsessing, it really is a distraction.  My hope is that it is  
just a flake of dirt or whatever that needs air-blowing off.  My worry  
is that the great cleaning it received was a bit on the vigorous side,  
and a piece of the silvering has now dislodged.  I wonder if anyone  
here can suggest a way of finding out which it is.  Being close to  
Christmas, I don't really want to send this back across the ocean (I'm  
in Japan) to Tony.  I don't have the tools to remove the top-plate.   
Is there a gap in the top-plate somewhere where I can try blowing a  
bit of compressed air through to see if the dirt flake, if that is  
what it is, dislodges?

I also discovered, now that I can focus, that the RF was not properly  
aligned at infinity.  I did this by focussing on a star against the  
black sky.  I turned the screw of the RF roller inside the lens mount  
area, and now that seems fine.

Thanks for reading!

Peter

P.S.  I have already considered just ignoring it, but the black flake  
really is a distraction.