Nord 2.451 to 2.631 were 0-4-2 locomotives for mixed traffic of the "Chemins de Fer du Nord".
The machines were retired from service from 1909 to 1923.
Construction history.
The locomotive design was first put into service at the "Chemins de Fer du Nord" in 1867 and originated from a similar design which was built by "Ernest Goüin" in 1851 for the Lyon railways and reproduced in large numbers by the "Chemins de fer de l'Est", "Chemins de fer de l'Ouest" and "Chemins de fer de Paris à Lyon et à la Méditerranée".
The main difference to these older types was the arrangement of the rear axle, which was supported from the outside in order to leave as much space as possible for the firebox between the wheels. 
The rest of the frame remained inside the driving wheels.
The Stephenson valve gear and the cylinders were on the inside of the locomotive frame.
The firebox was of the Crampton type, the boiler barrel consisted of three shells, with the middle one carrying the dome. 
A Crampton regulator sat behind the chimney, with the steam pipes running down on the outside to the steam chest.
The boiler pressure was on the first and on the later machines, with the earlier series later also receiving boilers for .
The Nord 2.451 to 2.631 locomotives were built by "Société J. F. Cail &amp; Cie" and "Fives-Lille" from 1867 to 1883.
The locomotives were coupled with 2 axle tenders, holding of water and of coal, and weighing .
References.
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