I can guess when and why they went. They were made by a company called Mackintoshes who were either taken over by, or were a subsidary of, Rowntrees. Rowntrees were in turn taken over by Nestle. If Goldencup Bars had survived Nestle's rationalisation of Rowntrees, they would have been ruined by cheap chocolate just like Nestle have done to another Mackintoshes bar - Toffee Crisp. May they RIP.