For the registration of its steam locomotives' fleet, the SNCF (French National Railways Company) adopted the system in use at the Paris-Lyon-Méditerranée Railroad Company. The first three digits indicated the number of load-bearing and driving axles from the locomotive's front to its rear. A classification letter and serial number followed. For the P to U series, the new plates were mostly made by reusing the brass frames of the old PLM plates. They were of smaller dimensions, 19 per 11 inches (485 per 290 mm), with sharp angles. All the models presented at the Cité du Train display one.