In the 60's and perhaps into early 70's PC produced some decent garments. I cannot recall if at the time they labeled them couture. I know I had purchased one, I believe at Saks, YSL being another, haven't followed the brands since then. I doubt if your garment dates that far back. Other than interest in knowing it's provenance, You seem to be describing a good quality garment and I would be happy with that. Many designers produce a high end garment as well as diffusion lines. The word couture is used rather freely by many designers. May or may not be indicative of quality but your seems to fall into the former.