Walt Frazier Enterprises was a landmark. It had an office on Park Avenue. Frazier was its namesake and its face. He owned a third of it. Billy Cunningham, then a 76ers star, owned a third as well. Irwin Weiner, the actual agent in the midst, owned the other portion. Together, they represented some of the league’s top players, from Julius Erving to George McGinnis and George Gervin, at a time when there were few agents even around. “They set the tone for how things are operating now,” Mychal Thompson, one of its clients, said.