Manual Help?

Not likely to be of any use.
Your 2M is a 1940 model based on the D4400 engine.
The 91G, 46D are 1964-1968 production machines based on the D330 engine.

I have never found any record of a Service manual or a Servicemans Reference Book being printed for any of the early 112's.

I am under the impression that Cat regarded all the late 1930's to late 1940's graders as being so similar (and relatively simple) in frame/chassis construction .. that you could use the Cat 12 manual or SRB from the same build years, for any repairs on the frame/chassis of the other models of graders.

This isn't a rare event, Cat never printed SRB's for numerous models of equipment.
The engine SRB for the D4400 engine (4¼" bore) will see you right for additional engine info .. and the SRB produced for the WW2 Cat 12 graders (Form 7401) provides enough basic information on the grader drivetrain, and power controls to see you right for any drivetrain or power control info.

Around 2/3rds of Form 7401 SRB, is related to engine and engine accessories info .. and about only a third of the book, just provides very basic drivetrain/power control info. These things aren't rocket science .. they are just driveshafts and gears, basic brakes, simple transmission .. all very basic stuff.

What confuses many first grader owners, is initially-complex-looking designs, such as the tricky setup of the power control shaft being located inside the transmission input shaft .. but once again, this isn't rocket science .. once you've got one apart, you don't need a engineering degree to put them back together again, unlike a German or Italian sports car.

That's the reason we love 'em, and why so many Cats from the 1930's and 1940's are still running, and working every day .. good old, robust, simple, well-engineered, American engineering, that was built to last, and to be repaired.

I realize that these machines aren't all that complicated, it's just that I would rather take the guess work out of some of this stuff & have it written down in black & white. But if there isn't a service manual available for this unit I guess that I'll have to go on without it. Thanks for all the assistance.