Starting in 1859, Mason built a total of 49 Ten-wheelers with a long wheelbase for the Lehigh Valley. The first one was No. 21 “Bushkill” built in July 1859 and the last one was No. 199 “Hamden” built in October 1874. The drivers had a diameter of 48 inches and the cylinders measured 17 by 24 inches. Before these, Norris had built two locomotives with similar dimensions in 1857. In contrast to most locomotives of this wheel arrangement, the Mason locomotives were connected to the first driving axle. The first ones were already rebuilt in 1874, but most only followed between 1886 and 1891. The last ones were retired by 1905. Only some rebuilt to the class J-5 survived some years more.
