Everything I have read recently indicates the major difference between an E-1 and an E-2 was the addition of the dorsal turret, but also that most surviving E-1's were upgraded to E-2 standard, and they E-2's were updated to E-4 status. I speculate that the A/C in the video is an E-1 in the process of being upgraded to E-2 standard. It would explain the different markings on the same A/C.
Just my opinion.