The Kopei Railway was a line in the Yunnan Province in southwestern China that had been built by the Gèbì Railway Company from 1915. The purpose of the line was the transportation of tin ore from the local mine between Ko-Kiou and Pi-Che-Tchai, what led to the name “Kopei”. It had a gauge of 600 mm, curves with radii of 70 metres, seven tunnels and was 72 km long.

The first locomotives on this line came from France, but the operator soon switched to ordering American locomotives. After some 0-8-0T tank locomotives delivered by Baldwin, they ordered the first batch of the model shown here. They had originally been ordered as 0-10-0T tanks with the coal bunker in front of the cab on the left side. But the order was quickly changed to tender locomotives. Baldwin designated the type 10-20-F.

Each locomotive weighed 64,700 pounds, had 28-inch drivers and cylinders of 13 by 16 inches. Although they were mainly used as pushers, they were equipped with Westinghouse air brakes. The first batch was delivered in 1924 and by 1929, their total amounted to 16. The first ones had a four-wheel tender with 1,000 gallons of water and one ton of coal. Later batches had six-wheel tenders with 1,500 gallons and two tons.

Although the line had been built for tin traffic, a new branch line connected an agriculturally rich district in 1928. The locomotives had been specified to be easily converted to metre gauge, but actually they were only used on 600 mm gauge until the end of their service life. The last ones were retired in 1990 when the line was actually converted to metre gauge.