Serial Number Prefix

(quoted from post at 05:43:14 02/11/18) My Massey 65 diesel has a 4 letter serial number prefix.
UNDM 704769. 1964 model from tractordata.com
Looking at my parts book doesn't seem to address this 4th letter. All the info I can find only addresses three letter prefix
What is this telling me?

From the the yellow underpaint it seems to have been decided it is a utility chassis. Is this a factor in the 4th letter?

My question is:
What does the UNDM mean?

Where do I find the transmission stamping?

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(quoted from post at 15:10:32 02/11/18) ptfarmer had one up on me. I couldn't find any info to conflict

Thank you Tony.
That makes all kind of sense. It never occurred to me.
U = Utility
ND = Diesel, Direct Injection (2 different letters for the engine section of the book combined into a 3rd letter prefix)
M = Dual-Reg. Transmission

I'll check the tires when it ain't falling a flood. Its a frog floating rain right now.

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(quoted from post at 19:25:07 02/11/18)

(quoted from post at 15:10:32 02/11/18) ptfarmer had one up on me. I couldn't find any info to conflict

Thank you Tony.
That makes all kind of sense. It never occurred to me.
U = Utility
ND = Diesel, Direct Injection (2 different letters for the engine section of the book combined into a 3rd letter prefix)
M = Dual-Reg. Transmission

I'll check the tires when it ain't falling a flood. Its a frog floating rain right now.

Click to expand...

What I found with the pre-fixes the N was for 4.192 Perkins diesel (BUT) I also found the D was for 4.203 Perkins diesel.

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