High Quality Content by WIKIPEDIA articles! The 1975 Commercial Union Assurance Grand Prix was a professional tennis circuit administered by the International Lawn Tennis Federation (ILTF) which served as a forerunner to the current Association of Tennis Professionals (ATP) World Tour and the Women`s Tennis Association (WTA) Tour. The circuit consisted of the four modern Grand Slam tournaments and open tournaments recognised by the ILTF. The Commercial Union Assurance Masters, Davis Cup Final and Nations Cup are included in this calendar but did not count towards the Grand Prix.