NWE Nos. 6 and 7, later Class 99.610, are narrow gauge tank locomotives with a C axle arrangement that belonged to the Nordhausen-Wernigerode Railway. The two engines had been supplied to the Army Technical Research Institute (Heerestechnische Prüfungsanstalt) but were transferred in 1917 (superheated steam engine) and 1921 (saturated steam engine) to the Nordhausen-Wernigerode Railway as NWE 6 and NWE 7. NWE 7 had previously worked as Locomotive No. 15 with the Nassau Light Railway. Only 99 6101 is currently in working order. * 99 6101 takes on water * 99 6101 heading a heritage train