Number 1051 is an Alco RF1A built in 1943 (builder #70675) for the U.S. Army, #8054.  The Alaska Railroad purchased it in 1947.  They retired in in 1964 and scrapped it in 1965-67.  The above photo shows #1051 with passenger train #5 at Healy, Alaska in 1952

Photo courtesy of James Sava
Retired Alaska Railroad Trainmaster