The Coahuila y Zacatecas was a Mexican narrow gauge (3-foot) short line that served a large copper mine and smelter at Concepcion del Oro, Zacatecas. The CyZ had just recently switched from steam to diesel power when this photo was made, so activity was at a minimum in the Saltillo roundhouse. Awaiting their fate, left to right, were 2-8-0 #12 and 4-6-0 #7.