In 1912, the Japanese Government Railways received three types of 0-6-6-0 Mallet locomotives from different builders. These were 24 of the class 9750 from ALCO-Schenectady, 18 of the class 9800 shown here from Baldwin and 12 of the class 9850 from Henschel. All three classes had similar dimensions. They were designed for lines with grades of up to 3.3 percent and curves with a radius of 120 meters. Anyway, their drivers with a diameter of 49 inches or 1,245 mm looked relatively huge in comparison to the size of the locomotives.

The diameters of the high pressure cylinders was between 15.5 and 16.5 inches, with 16 inches on the class 9800. The high pressure cylinders had diameters between 24.5 and 25.5 inches, also here the 9800 was in the middle with 25 inches. All cylinders had a stroke of 24 inches. In the end, neither these 0-6-6-0 Mallets nor other 0-4-4-0 Mallets couldn't persuade the decision makers in Japan, so their number stayed relatively small.