MM U was made from 1938-58. Major production numbers. Early ones had red grill and seem to be more collectible. UTS (standard axle) more common in wheatland. UTU(universal or narrow front) common in row crop areas. There also was U diesel,cane tractor UTC, extendable axle UTE,UTN single front wheel all very collectible. UTI or UTIL was the industrial version. The UB was later 50's with raised platform and foot clutch. Value is determined by location ,condition and style. Hard to put a value unless model is known as well as serial number.