GRANDMASTER CHESS WAS PUBLISHED IN 1982 BY KINGSOFT and distributed by AUDIOGENINCS. At that time it was the strongest chess game available for the Commodore 64.
Complete instructions are provided in the game.
You can read about the original GRANDMASTER here:
The playing strength of GRANDMASTER CHESS is approximately 1300-1400 ELO (1500 - 1600 USCF).