The model S-12 was the sucessor to the DS-4-4-1000. Production ran from mid-1950 to 1956. By 1955, B-L-H began the phase-out of diesel-electric production. During this period the supply of Westinghouse electrical gear for the switcher line became depleted, forcing Eddystone to begin using General Electric main generators and traction motors. Between the time in 1953 that Westinghouse began contemplating its discontinuance of railroad electrical equipment and the time B-L-H decided to go out of the diesel-electric business, a new, 6-inch longer frame was designed to accommodate the GE gear. The frame was also modified so that the end steps and pilots could be built separately and bolted on rather than welded. By 1956 the end was at hand and with the departure of Erie Mining Co. S-12 403 (October, 1956) after its use in testing the New Haven RP-210s, the book was closed. With the erecting halls shut down, the final tally of the S-series switchers could be made. There had been 63 S-8 switchers sold to 16 customers in a production run of three years, nine months. In six years and one month of S-12 deliveries, 452 units had been delivered to 48 original customers.