Serial number code ID

[D Ervin]

I have a late 1953 Stage II Farmall Super H. The end of
the serial number, after the numerical digits, end with the
letters D M J. What does these letters stand for?

 

[used red MN]

From the horses mouth in a manner of speaking. In the link click General, then click the Quick View of sub-section 237. It shows D as 5000 ft High Altitude Attachment which is basically higher compression pistons. And J is the Rockford style clutch. Your ..M.. suffix seems to be a mystery, some other guru may have an answer for you. If not obvious, from the link you can view all the parts sections for your tractor.
CNHI Super H online part diagrams

 

[Bob M]

D = 5,000 ft altitude pistons (higher compression)

J = Rockford clutch

M = special lower transmission gearing

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J is very common - perhaps universal for the Super H(?)

D and M are less common but are still out there (my stage I '53 SH has both the D and J suffix).

 

[D Ervin]

That answers my question! I really appreciate the info!