Advice on RF calibration in SM Leicas?

[Alexander Finkelstein <obender@ibm.net>]

Sirs/Mesdames(NB: are there any here?),

I'm new to LUG (have been lurking for a month) - forgive, if I raise
topics that
have already been discussed.

It seems that my grandfather's FED (russian LeicaII knock-off) has
finally given
up the ghost and I have to get a real issue. It won't be named after a
Grand 
Inquisitor (FED stands for F.E.Dzerzhinski), but I hope it'll be better
made. 
Methinks, a postwar IIIc or a IIIf should do. So my first question is:

1. How can one check the RF calibration in a store, where distanses to
objects are
not known? I hear that many outfits claim to have cameras adjusted when
it's not 
really the case.
I have an idea. I got a well calibrated lens, Jupiter 85/2 (not at all a
bad one,
it's based on Zeiss Sonnar). I mount it and stand in front of a mirror.
Focus on
the mirror edge/frame, note the reading, then focus on lens in the
mirror, again 
taking the reading (must be X2, of course). Repeating the procedure from
several
points should expose any systematic error, since the scale is non-linear
(parabolic ?). Obvious problem - the mirror curvature and other
distortions, 
introduced by it. Will it render the whole rigmarole useless? Any other
pitfalls?
Other ideas? 

2. That brings me to another heretical question: is precise focusing
possible on 
a Leica? (Please don't unleash an angry fusillade that L is the best;
this we 
already knew). L is supposed to be an available light camera with lenses
that 
produce good results when wide open. Let's say I'm focusing my 85/2 on
an object
2m away. At that distance and aperture 2.0 the depth of field should be
about
+/-1cm (I don't remember the formula by heart). I have an excellent
eyesight
(used to see all rows in the test table) and I would have a lot of
trouble
focusing in an ideal situation. How one can focus on a victim's eyeballs
and not
eyelashes in low light with somethinglux 75/1.4 that Leitz makes (even
less DOF)
is beyong me.
But that's not all. What about mechanical reliability of RFs and lens
mounts? 
It's hard to imagine that 40 or 60 years of wear and tear would do to
the
extremely precise and fragile mechanism of RF, where hundredths of mm
count.

3.Recently, when I was looking at a IIIf, I noticed that the
spring-loaded RF
"arm" (not sure what it's called in English) has a roller disc on its
end and
not an eccentric as I would expect. I don't want to spill graphs and
formulas
into this letter, so can anybody enlighten me as to where info on RF
workings
can be found? I mean math functions that describe all these gearwheels,
racks 
and pinions.

BTW, if somebody is selling a good IIIc or IIIf (look is not very
important),
let me know. 
Or, maybe, some can advise on good stores to buy from.

Thanks for your time.
							Alexander Finkelstein