This is an early production (Phase 1) H-16-66 and is riding on Baldwin 13 foot wheelbase rigid-bolster, fully equalized trucks, which were actually General Steel Castings Commonwealth C-type trucks. The Phase 1 H-16-66's were equipped with Westinghouse electrical gear (Model 370-F traction motors on each axle). Later H-16-66 production units were equipped with GE electrical gear and rode on F-M's Tri-mount drop equalizer trucks designed for the Train Masters built in 1953. The H-16-66's were known as "Baby Train Masters" (note that Train Master is two words), and produced 1600 horsepower from eight cylinders (16 pistons in the opposed-piston design).

In 1950, FM had, at C&NW's request, modified its old-style H16-44 design to the H16-66 configuration. It amounted to a custom design; however, except for the six-motor switch gear and the small changes to the underframe for the six-wheel trucks, FM got by with its standard H16 design. The truck had already been designed, being the one Baldwin used for its various C-C units. It was a truck that looked, and rode, like something that had been rescued from a steam locomotive tender, vintage 1930. But the C&NW was satisfied with it and purchased 25 of those H16-66's, not a bad deal for FM. In the Train Master era, Milwaukee Road came to the time for dieselizing its branch lines, so in response to that need, FM scaled down its Train Master to create the new-design H16-66. The C&NW bought some of those as well.

I have a theory about those scuff marks in the dark paint below the Engineer's window. This locomotive is equipped with what was known as a "toe step", a piece of angle iron attached to the cab to allow maintenance people to walk from the cab door to the windshield by means of this step. Given the lack of grab irons between the cab door and front, I imagine a lot of maintenance people lost their footing and that's the marks of a men in trouble. The CB&Q had a similar arrangement on the Fireman's side, and also provided a grab iron mounted just below the cab window that ran the length of the toe step.