If I did not yet have an Assist, then it would have been one of the several Rescue models I have carried for the past couple of decades. I think this is before I started carrying a Gunting,in addition to the Rescue/Assist, because I think the Gunting came along after 2001. (I know I was EDC-ing a Gunting by early 2003, when I traveled to a seminar taught by Bram Frank in April.)
I do know what I was doing the morning of September 11, 2001. The garbage collector truck was late, and for some reason I was late getting in bed, after working a night shift, and took the opportunity to do some extra cleaning, in order to put more into the trash container. We were scheduled to move later in the month, so were constantly going through things that should be donated, sold, or thrown away. My neighbor, Howard Miller, walked from his front door, and asked me if I knew two airplanes had crashed into two buildings in New York City. My first thought was "terrorists." There was not a second of denial. I had been expecting suicidal terrorists to hijack an airplane, and use the airplane as a guided missile, since the late Seventies.