Thanks for all of the info but I think it is just as it is supposed to be. I found a couple of resources that have lists of numbers and it wasn't until 1948 that the RT(X) designations really came into affect. For instance here is an example:
http://jetstar.minneapolis-moline.com/MM-Louis_serials.txt
RT TRACTORS
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1944 409358 - 410757 inc.
1945 410748 - 413754 inc.
1946 413755 - 416544 inc.
1947 416545 - 422057 inc.
1948 (RTU) 0014800001 - 0014802402 inc.
1949 (RTU) 0014900001 - 0014903039 inc.
1950 (RTU) 0015000001 - 0015002155 inc.
1951 (RTU) 00102156 - 00103972 inc.
1952 (RTU) 00103973 - 00104823 inc.
This list does not call out RTU specifically until 1948 when the serial number sequence changes. Mine fits into the 1947 row before the 00 was added to the serial number. On another list:
The Model "R" Series M-M Registry List
There is a comment that the RTU from 1947 (serial number listed is one later than mine) that it has a wide front end.
RTU 421507 U Has wide front end
So I guess the answer is that this is an original 1947 RTU but not really considered the RTU yet... Best I can figure...