It is, in fact the post code and it pinpoints the house with great precision because the second name, Lantabat refers not to a village, but to a valley.
Lantabat is in Basse Navarre, one of the three provinces that make up the Pays Basque, which is the French part of the world populated by Basques.
Indeed, this has been an area famous for its walkers since the Middle Ages: not far from Lantabat is the town of St Jean-Pied-de-Port which has always been a resting place for French pilgrims on their way to Santiago de Compostela.