I use the M-Coder from matchtechnical.com. I code it as a 1994-2004 Summilux 1.4. the M-coder uses a black felt pen 0X0XXX0 X is black, o is blank. There is a screw under one of the black marks so every 10-15 times you mount the lens you need to re-mark it. No big deal. the m-coder is easy to use. The camera will not register 1.2 since the Summilux only goes to1.4. I don't think this is a big deal. Also I use a B&W filter, not the Leica brand (cheaper). Set the camera to lens recognition/UVIR. Works great! I have 6 lenses coded this way.