The late 80's/early 90's  was the turning point on many fronts for sail makers. New materials like monfilm and changes to sails to include CAMS were becoming common.  While Im not 100% sure...I believe the Gaastra Speed/Slalom on this page is from 1991. I purchased this one and had the mylar window replaced (as it was getting brittle) with PVC

There were several sails made by Gaastra from 1988 - 1991 that look similar so it has been difficult to precisly date this on. The construction reminds me of an earlier model (1988) but I couldnt quite find anything that looks like it. The video at the bottom of the page give the closest indication of the date of this sail