big shiny noses and portholes were imitated in the styling of UP's E2 locomotives from 1937. Each power car had a 1,200 hp V16 Winton 201-A engine, generator, and a pair of two-axle powered trucks. The rear truck of the first power car and the lead truck of the second power car carried a span bolster to which both power cars were articulated, so they made one unified locomotive of B-B+B-B configuration and a total of 2,400 hp (1,800 kW). M-10004 was matched with a trainset of tapered cross-section, low profile articulated cars of the type built for the earlier M-1000x trainsets. The first cars had been built in anticipation of another tapered turret cab locomotive, but Union Pacific decided instead to cancel the proposed turret cab, expand the set to nine cars, and match it with a more powerful locomotive set of the newer design. The lounge car of the M-10004 set was also built with a food preparation facility occupying its blind rear, which was revised with a new layout and porthole style rear windows between the train's City of San Francisco and City of Los Angeles service periods. The M-10005 and M-10006 trainsets were built straight-sided to increase interior space, semi-articulated, and shorter by two sleeper cars than the M-10004 set. All of the M-1000x trainsets were lower profile than standard passenger railcars. Changes The most significant change to the City of Denver power sets came in 1939, when they were converted from two-car, 2,400 hp sets to three three-car, 3,600 hp (2700 kW) sets using power equipment from M-10001 and M-10004. Other changes included a gyrating signal light installed below the main headlight after the Second World War, the loss of the stainless steel trim on the pilot, the addition of the Chicago and North Western Railway herald to the nose in addition to the Union Pacific one, and changed nose-side badges for the route. The original Armour Yellow and Leaf Brown livery was changed incrementally to the modern livery of Armour Yellow and Harbor Mist Gray roof and base, with red trim striping separating the main colors. That same footage shows two boosters in the power set, indicating service as City of Denver with the expanded M-10003 (CD-07) power set, and an eleven car consist, expanded from the original nine car consist with cars from either the M-10001 or M-10002 set. Slate gray was replaced