No. 7107 is an Alco S-2 built in 1943 (builder's number 70266).  It (and three others) were obtained from the US Army in 1955 .  Number 7107 was retired when it was destroyed at Seward in the earthquake on March 27, 1964.
Photographer Gene Adoline was an enlisted man in the Army at Ft. Richardson in 1954.  Of his photograph, he recalls, "Number 7107 is loading up a troop train outbound at 'O' Street, Elmendorf."
Photo courtesy of Gene Adoline