[Leica] Horizontal Rangefinder Adjustment on M - what is the secret?

["Stephen Attaway" <attaway@slip.net>]

Esteemed LUGers:
The rangefinder on my M4P is off by a tiny bit at infinity, just enough to
notice two lines where only one should be when focused on a distant
flagpole. I sent it in to Gasser's, who checked it and said it looked ok.
Yet it still bugs me. Does this small error make any practical difference?
Its pretty clear to me the adjustment is not made in the same way as a IIIf
or a Canon7, as there is no adjustment screw where I expected to find one.
I looked up rangefinder alignment in the archives, and found that the screw
that was not there would have adjusted vertical alignment, had I owned an
M4, M3 or M2. So I am glad I did not find it, in a way. Someone, I believe
it was Mark Small, stated that horizontal alignment was "user adjustable and
required a special tool". It looks like there is an arm to adjust an
eccentric on the pivot for the rangefinder cam.
Can anyone tell me the procedure for adjusting horizontal alignment on the M
and what special tool is needed? Of course if the procedure is to ignore
small errors until a CLA, I can live with that.
Kind regards,
Stephen Attaway