with Harbor Mist Gray at some point after the mid-1940s. A publicity photo of M-10005 from 1949 shows the trainset with a Harbor Mist Gray roof and a single headlight. Individual power set histories The demands of long-distance high speed City train service taxed the ability of the M-1000x fleet to meet them. The original 2400 hp power sets with Winton 201A Diesel engines were underpowered for their service requirements and had a short lifespan for mechanical parts, with at best 100,000 miles between piston replacements. These shortcomings led to various measures including equipment replacements, 50% redundancy in locomotives assigned to the Denver run, consolidating the motive power of locomotive sets for a 50% boost in power for the remaining sets, and using a locomotive set built for full-size trains instead of the type originally matched with the trainset. M-10003, later CD-07 Despite the earlier number, the M-10003 was actually the last completed of the four. This was because the number M-10003 had been previously assigned to a projected sister trainset to M-10001, which was cancelled when Union Pacific sought a longer trainset with more power in order to meet demand. The number was reassigned to the fourth of the new locomotive sets. The M-10003 was intended to be a spare power set, able to fill in on either the City of San Francisco or City of Denver if any of the other three locomotives needed maintenance. As of March 7, 1937, its booster unit was on loan to M-10002 on the Los Angeles run. In June 1937, it was decided to permanently assign it to the City of Denver and it was renumbered to CD-07. A third power car was added in 1939, the converted M-10001 power unit. CD-07 remained in service on the City of Denver with the two other sets until March 1953, and was scrapped with them in summer that year. M-10004, later LA-4 First completed was M-10004 in May 1936 for the City of San Francisco. The new power cars had vertical sides and higher profiles than the previous streamliners, but the rest of the train was built to the tapered-side profile of the M-10000 through M-10002 sets. It entered revenue service on June 14, 1936 but lasted only 18 months on the route before a train equipped with the new EMC E2 3-unit set SF-1, SF-2 and SF-3 took over that route. The train