The last two built, GTW 1950 & 1951, had a narrow lip on both ends and as far as I know they were the only two like that.
Steve
Steve is correct. Jerry Pinkepank's The Second Diesel Spotter's Guide advises:
"Variations: Two units built for GTW in 1957 (the last domestic RS-1's built) had roof metal protruding about 2 inches over hood ends in a lip rather than a rounded edge. Prewar RS-1s converted to E-1645 RSD-1's were NYSW 231, 233; MILW 1678, 1679; RI 746-749; ASAB 901-903; TC&I 600, 601. NYSW got different postwar RS-1's of the same road number." And the same book later advises "However, the basic elements of this useful machine were unchanged after 17 years of production: by far the longest production run in U.S. dieselization for any single model."
Bill