10/31/2006. Remarks by Jack McKillop: "This is a P-61B-15-NO. One of the major modifications on this model was the return of the remote-controlled dorsal turret with four .50-caliber (12.7 mm) machine guns. The original P-61s were designed with the turret but it had been removed on the 38th P-61A and the first 195 P-61Bs because of 'a vibration problem when the guns were fired' although the real reason may have been that the turret had a higher priority in the B-29 Superfortress program."