Though originally numbered 8 & 9 upon their import from the United States, the two locomotives were re-numbered 9 & 10 upon their sale by the government-controlled Horonai Railway to the Hokkaido Colliery and Railway Company in 1889.

Three years later, legislation would formalize and standardize the numbering, establishing the Class 7170 as consisting of these two locomotives, dubbed 7170 and 7171.

At this time, the chimneys were altered, and the forward sections of the steam rooms expanded.

Though they served their new purpose well, and were used extensively, one of the locomotives suffered an accidental collision on July 2, 1950, and was scrapped the following year.

Like the 7100 series, they bore a diamond-shaped chimney and cow catcher in the older American style, but had straight-top boilers instead of wagon-top ones, and a steam-dome in the second boiler compartment.