Originally Posted by Ko.Fe.
I used one manual from Brian Sweeny, but could find it anymore.
Basically with J3 you need to remove entire lens block from focus assembly and on lens block you will see shimming ring. I'm using it as template and cutting additional from paper. Most of the times I need to add one.
Only tricky part is to shift focus scale ring after it. It requires drilling three new locations to where three holding screws will screw in.
Those three screws are extremely small...
I've found Brian's guide https://rangefinderforum.com/forums/...4&postcount=15
My cunning plan is to have a very skilled friend who is insanely capable of dealing with tiny screws to do the job. He doesn't know this yet, but he owes me...
Film amateur with a few rangefinders - Leica III, M2/M3, Werra 3 and Zeiss Super Ikonta 534/16 medium format.
Apart from that have a Rolleiflex 3.5F, the odd Minolta XD7, Hasselblad 500cm, a Topcon Super D and an Intrepid 5x4 large format (not the half of it but I am clearing them out, honest).
I do all my own black and white developing at home.