 Some sources record these locomotives as X14 class, and this designation was sometimes used to refer to the longer-framed versions, but for most purposes the two sub-classes were grouped together and known as M7.The 1904/05 construction batch moved the sandboxes back to the front splasher and new items were feed water heating, single ram pumps and balanced crank axles.For the remainder of construction from the outshopping of the 105th locomotive in 1911, duplex pumps were fitted.