I see that IBDB lists a 1965 Vivian Beaumont production of Danton's Death as its first acknowledged production.
I was once in a group of actors (eating!) discussing all these various contracts and their acronyms, like LORT etc. The actor Richard Woods, who had just performed at Williamstown, said that at Williamstown they had an FTA contract. Others question what that was. Richard explained: "F*** the actors."