The major difference in appearance between Southern Pacific's GS-3 and GS-4 Northern-type steam locomotives was the front end. The former had a single headlight on the conical-shaped, silver-painted smokebox front, while the latter sported a conventional light plus an oscillating Mars headlight, whose purpose was to attract motorists' attention at crossings. No. 4455 pictured here in Los Angeles on January 8, 1955, is a fine example of the GS-4 class, numbering 28 engines from 4430 through 4457, all Lima-built machines of 1941-42 vintage. Photo by Stan Kistler/Southern Pacific Railroad Publicity Department and my collection.