Era IIId (1961-1970) and IVa (1971-1979).
This implies:
See an interesting topic in the Loco-Revue forum about the seventies.
International Union of Railways
(Union internationale des chemins de fer).
On Wikipedia, see marking for freight cars,
for passenger coaches.
SNCF Division d’études des voitures
Unifiée pour service intérieur
Defined by Union internationale des chemins de fer
International Sleeping-car Company
Trans Euro Night