The devel-docs about METH_CLASS:

The method will be passed the type object as the first 
parameter rather than an instance of the type. This is 
used to create class methods, similar to what is 
created when using the classmethod() built-in 
function. New in version 2.3.

The code does not do it in this way. The first 
parameter the function receives is NULL, the type 
object goes together with the remaining arguments
in the second parameter (which is a tuple).

See the thread with subject 'METH_CLASS' on python-dev 
at 2002-04-25, Guido agreed that this should be fixed.