WHEN PORSCHE BEGAN PRODUCING THE TARGA IN 1967 IT WAS DESIGNED WITH A SOFT VINYL REAR WINDOW.  THIS WAS REPLACED IN THE MIDDLE OF THE 1967 PRODUCTION YEAR WITH A GLASS WINDOW.  THE LATTER STYLE HAS PERSISTED TO THE PRESENT.  ONLY 500 OF THE SOFT WINDOW VERSION OF THE ORIGINAL TARGA WERE PRODUCED.  CONSEQUENTLY, THIS IS A RATHER RARE MODEL.