For some reason some (IMHO useful) tables in the CIL specification (ISO/IEC 23271, Second edition from 2006-10-01) are not documented. These are mainly the AssemblyOS and AssemblyProcessor tables. As I'm working on finishing the MOSA ahead of time compiler to finally be able to produce bootable images, I think these metadata tables are very useful. What really makes me wonder is that even the constants for these tables seem to be documented. The rdwProcessors field is an array of processor types as defined in winnt.h and the OS version is the same as usually encoded in unmanaged Win32 OSVERSIONINFOEX.
I guess it's time to visit the ReactOS project and to pull these constants out of their repository.