Bessa-RF-top-access by
johnnyh4, on Flickr
Carefully prise the soft aluminium DOF disk off with a fine-pointed tool - it is glued to the dished washer underneath via a paper disk.
Remove the screw retaining the dished washer to the thumbwheel assembly.
Carefully prise up the leather at the far end and remove the screw revealed.
Remove the hollow screw to allow removal of the rest of the thumbwheel assembly - making note of all positions ;-) .
This gives a picture showing the adjustments. "Achtung!" here is warning you not to turn the focus closer than the normal minimum distance, after you have removed the stop-washer, as the lensboard rack will come out of it's engagement with the pinion, and it warns that re-assembly is not trivial.
(I had one of these which came with the lens a long way out of focus, yet the rangefinder itself was spot-on. Evidently this had happened to a previous owner, and it had been incorrectly re-assembled. It was not as it left the factory, as the paper disk mounting the depth-of-field disc was missing, just glue had been used.I was able let the rack emerge, turn the pinion a tooth or so as required then re-engage the rack and re-assemble.)