[Leica] Hey Walt! Rangefinder Check?

[Rick Dykstra <rdandcb@cybermac.com.au>]

Hey Walt!  Can you comment on this little method I've tried for checking the
accuracy of my M6 rangefinder?

I take the camera back off, replace the bottom and mount the camera on a
tripod, put on a 90mm lens and point it at the ground from a bit over a
meter up.

I lay a ground glass screen flat upon on the film guides (the inner one of
the two at the bottom).  Yes, it's a bit fiddly to do.

I lock the shutter open with a cable release.

Then, I focus on something like a barcode laying on the floor and check the
focus on the ground glass with a magnifier (lens wide open).

So Walt (or others), should this work or is the ground glass not in the
right position?  Any help would be appreciated.

Thanks!

Rick Dykstra