The quick and easy way is:

FW 400 = OS 9 is

FW 800 = OS 9 is xx(

Longer:

The MDD came in three revisions:

2002(FW 400):

G4/867 MHz dual,

G4/1.0 GHz dual,

G4/1.25 GHz dual

NO OS 9 January 2003(FW 800):

G4/1.0 GHz single,

G4/1.25 GHz dual,

G4/1.42 GHz dual

June 2003(FW 400):

G4/1.25GHz single

G4/1.25GHz dual

I don't know the identifier numbers, so based on speed it could be any in italics. If it is a single, it is an '03 MDD(FW400) and will boot 9 fine. If it is a dual, you'll need to see if it is FW 400 or 800.