This weeks offering from the Flight International Space Archive
Ariane 5 EAP/EPC mock-up assembly during MDO 1 campaign in Kourou, Autumn 1993 .....
EAP : Etage Accélérateur a Poudre = Solid Rocket Booster
EPC : Etage Principal Cryotechnique = Main Cryogenic Stage
MDO : Maquette de Deploiement Operationelle = Operational Deployment Mock-up
Congratulations rapier you are exactly right it is the Ariane 5 EAP/EPC mock-up