The Arnold Jung Lokomotivfabrik in Jungenthal, Germany delivered two four-axle Mallet locomotive G 2x2/2 no. 4 and 5 with the names of Pouillerel and Spiegelberg for the commencement of operations of the Saignelégier–La Chaux-de-Fonds line in 1892. The first revision was obtained in 1894, when a third locomotive Franches-Montagnes was procured and given the number 6. In 1900, Jung delivered the last locomotive, no. 7, Jura. The numbers 4 to 7 continued on from the locomotive numbers of the Ponts–Sagne–La Chaux-de-Fonds Railway, as the two companies had an operating arrangement.
