Anyone know Minn. Moline Tractors?

Hey Guys,
I'm trying to figure out what year and model this tractor of my uncle's is. Obviously, it's a minneapolis moline, and I'm pretting sure it's an R or RT, but not sure if it's an rti, rtu, rts, or what. It has the 3 5/8 x 4 4cyl with a foot clutch/throttle as well as the hand ones.

Any help would be appreciated since I've spent hours looking at pictures etc. I can't read the body S/N tag because it's worn, but the engine tag is pretty legible.

Thanks,
-Travis-