[Milsurplus] TM numbering structure

[J. Forster]

Some time ago, I saw a list of how the suffix numbers of TMs were structured,
but can't find it. Can anyone enlighten me:

My interest is the following:

TM 5820-1234-xx

What does the -xx signify? I'm pretty sure -34 is a parts ID document and -35 is
the schematics and maintenance information.

Thanks,
-John