The real early '64/65 have a shorter frame. The space between the seat tube and the brake bridge is smaller 2 inches compared to the 4 inches on the longer frames. The style of handlebar is also a give away. The first years used a real wide set of apes 31 inches, the following set in '66/'67 had very dramatic down turn to the grip pertion of the bars and then the went to a less dramatic bend. In '69/'70 they went to the bars that were basically straight up with very little v shape to the bars. The real early bikes had a Schwinn style sissy bar that bolted to the axle not to mounting brackets. Also there was a high loop sissy that was only '66/'67 I think, and the part behind the seat sticks way up. Any square backed sissy bar is very early. A first generation would have short frame, square back sissy bolted to axle and the real wide bars.Any pre '69 would have a wingtip style guard.