Using condensed milk to make slices was a lot more common back 1980s than it is today, but it certainly makes a nice slice. The first time I cooked with pecans was around that time as well. I made an ‘exotic’ American Pecan Pie, using pecans and the hard to obtain ingredient, corn syrup. I think this slice recipe probably dates from a little later than that, especially as it comes from an ad for Riverside an Australian company which urges readers to join the All Australian Pecan Club.