represented an important step in the evolution of the passenger diesel locomotive. While the EA, E1 and E2 were each built for a specific railroad and train, they were largely identical mechanically and were a step further away from the concept of custom-built motive power, integrated into a particular streamliner; and towards mass-produced standardized locomotives. This transition was achieved with the E3, E4, E5, and E6, EMC (later EMD)'s next models. Styling The E2's profile was more aggressive than the sloping snouts of previous EMC passenger power, so they gained a "bulldog nose" nickname. Subsequent blunt-snouted passenger units are sometimes also called this, but the E2's nose is by far the most bulbous among the E and F series locomotives. The seven porthole windows on the sides were one less than its predecessors in Union Pacific's diesel streamliner fleet, the M-10003 to M-10006. One of the nicknames that these locomotives acquired, because of these portholes and prominent nose, was "Queen Mary," after the British Cunard liner had recently been put in service. The Union Pacific Railroad also referred to the schedule of the "City of San Francisco," a passenger train hauled by these locomotives, as sailings. Later E units for Union Pacific, including E7 locomotives, were ordered modified with extra porthole style windows. The units were painted in Union Pacific's Armour Yellow with Leaf Brown roofs and undersides, the same colors as UP's previous streamliners (the M-10000 etc.). Color photographs indicate that UP modified their color scheme with slate gray roofs around mid-1941. There was extensive stainless steel on the noses, upon which were displayed the owning railroads' heralds in color. The bulbous nose and stainless steel ornamentation of the E2 evoked the nose design of the UP's M-10003 to M-10006 streamliner locomotives, which were also bulbous, featuring a large stainless steel grille and pilot ornamentation. UP's advertising from that era often had renditions of their locomotives emphasizing their bulbous and shiny noses. Replacement All four "B" units (SF-2, SF-3, LA-2, LA-3) went to the Union Pacific; they were used until 1953, when they were "rebuilt" into E8 locomotives. These rebuilds utilised little of the previous locomotives and were effectively trade-ins. The driving "A" unit of the SF set, SF-1, (the "Queen Mary") went to the Southern Pacific; it was likewise "rebuilt" into EMD E7 #6017. The "A" unit of the LA set, LA-1, went to the Chicago and North