Another vote for the coder kit, if you use the "calibration procedure" Scott mentions earlier in the thread. I had to recode my 50 Summicron on vacation when the black marks wore down a little (the first time it's happened in a year). Easy. I just made the marks through the coder, then took it off and thickened them in the correct direction, and voila. It took all of two minutes to do. I already have a dab of white nail polish in the screw head that's where a white mark should be.
The Japanese industrial marker pen that comes with the coder kit is oil-based and appears make marks that to be a bit more durable than a Sharpie. But in the early days of the coder kit the maker got a batch of pens that tended to dry out quickly. This is, I think, the cause of some of the complaints. A Sharpie works fine, the marks just wear off a little faster.
One suggestion I have is to turn the lenses to the locked position without applying downward pressure (towards the camera). This seems to make the marks less prone to rub off, as they don't rub on the camera mount until much later in the turn.
Obviously, the Milich adapters (for LTM lenses) or getting your lenses coded by Leica or milled by John Milich are more permanent solutions. You have to weigh the slight inconvenience of the hand-coding against the cost and time without your lenses and the reports of lenses coming back from Leica focusing less well than they did originally.
--Peter
