'Månesten', or 'Moonstone series, designed by Lütken in 1966. Yours were produced 1976.
HG + number was the method of signing glass from 1972 until the 1980s (although 1972 was HGX to stop confusion with pieces marked as seconds (typically marked '2' or 'II')), thus HG6 = 1976, HG7 = 1977, HG80 = 1980.