The APO Telyt is a wonderful lens on the M8. So far as I know there is no coding for this lens. There have been no back focus problems either (although I did adjust the focus on the M8 with the hex wrench method). I do use the 1.25x magnifier, and the best you can do for framing is an approximation of twice the focus rectangle.
It is simply the finest lens I own for Leica. Here are some samples:
http://web.mac.com/robert.rose/iWeb/Site/Yosemite.html
The APO Telyt was used for the L1000636 and L1000867 to L1001010 pictures. The other L pictures are Tri-Elmar, and the DSC pictures are from a D2x.
Regards,
Bob Rose