I found this rather interesting description: "This 80-ton diesel-electric built by General Electric started service at a US Naval Station before being transferred to the Atomic Energy Commission Nevada Test Site at Jackass Flats. It was then routinely used to haul trains carrying nuclear rocket motors between test stations at the Site." Full story here: http://www.waymarking.com/waymarks/WMFA3K_Jackass_and_Western_GE_80_Ton_Type_L_3_Boulder_City_Nevada
That's a great photo, Russell - nicely framed with a big sky and tracks going far away to the horizon.