1973 design, modified for the production run by Anderson Bros. from about 1975. Not many made. A 1979 one would have been a late build. Very quick for their day, especially downwind; custom versions won the '73 and '75 Hobarts. They had much cleaner lines than the typical early '70s boats.
PS - if you are looking at the green one please add in the cost of a new prop - three bladed fixed props are for powerboats only!