Ten narrow-gauge Class S 152 locomotives were delivered new to the D&RGW in September and October 1923 by the American Locomotive Company (ALCO) of Schenectady, New York. ALCO numbered them from 64981 through 64990. For the record, D&SNG #473 is 64984, D&SNG #476 is 64987, and D&SNG #478 is 64989. The Rio Grande reclassified them early in 1924 as Class K-28, but they kept their original builder numbers. These details are mounted on the smokeboxes (engineer's side) and can be viewed during the layover in Silverton. The locomotives were so successful, Rio Grande bought 10 more from Baldwin and rebuilt 10 more from standard gauge switch engines.