Number 1504 (B/N 17712) was one of the units from the first order (1952). 1500-1506 were ordered direct from EMD. On F7 units, all the even numbers are A units and all the odd numbers are B units.  These units were retired in 1983. (Denali National Park, 7/6/71)
Photo courtesy of James Caflin
Dean Motis Collection