This is actually the lower compartment of a T2 type car. These have always been marketed as 1st-class (then Preferente) accommodation in Spain, unlike in France and Belgium.
02nd October 2003. Photo by Albert Maestre (a448@tranvia.org) (Acknowledgements), from Tranvia.org Posting and Comment by P.L.Guillemin (plguillemin@yahoo.fr)