So KTM made models both for Max and USH. There are slight differences in most models - the SP Mountain mechanism only changed the gearbox and axle diameter. The Max PRR K4 is distinguished by a correct boiler taper. The USH copied the incorrect taper in the MRR Cyclopedia. Under $200 is a good deal for either, although the Max K4 is usually in that price range.
The one that really dramatically changed was the SP AC-12. Max used the wrong size drivers!
KTM is Katsumi Moketein - forgive the spelling; my Japanese is non-existent.