Ryan Toews adds:
"The 202 Kōkūtai is said to have changed its unit designation from "X" to "X2" in June of 1943. This Zero appears to have the tail code of X-133 and has the dark green upper camo used by Nakajima starting in April/May.
It also has servo tabs. Gakken 33 provides a serial number (A6M2 91113) and a date of manufacture (9 June 43) for Tora-110. Photos of that plane indicate no adjustable aileron trim tab. The A6M2 Zero 51553 has servo tabs and an estimated date of manufacture of early September 43. Evidently the use of the adjustable tabs must have begun from between these two dates.
Thus this A6M2 Zero must have been manufactured sometime just after 9 June and was therefore one of the first to incorporate servo tabs. Or, more likely in my opinion, the tail code prefix of "X" actually should be "X2". This would fit much better into the dates at which the 202nd Kōkūtai changed their identifying tail code and the adoption of servo tabs."
Jim Long adds:
"This Nakajima-built A6M2 Zero was one of those that had reintroduced the aileron servo tabs. These aileron servo tabs were used on a few early A6M2s by Mitsubishi in an attempt to increase the rate of roll. But they were implicated by a crash investigation as being at least partially responsible for the break-up of the plane in question.
They got a bad reputation and were removed from the rest of the A6M2s by Mitsubishi. When Mitsubishi designed the Model 22, the engineers reinstated the servo tabs because rate of roll was still unsatisfactory. On the Model 22, the servo tabs met with better success.
Since the servo tabs were working well on the Mitsubishi Model 22, Nakajima adopted them during the time frame suggested by Ryan for the remainder of their production run of A6M2s. Since the Model 22 had the servo tabs and the late-production Model 21 by Nakajima did too, we have to be careful about identification. If we see these servo tabs, the plane could be an A6M2 by Nakajima or an A6M3 Model 22 by Mitsubishi.
Servo tabs cannot be adjusted in flight from the cockpit by action of the pilot to trim the ailerons. They, therefore, are more properly called servo tabs or flying tabs rather than adjustable tabs. They operate by linkage which is arranged to cause the tab on each aileron to move in the opposite direction from the aileron, thereby assisting to move the aileron by aerodynamic forces.
The servo tabs on the A6Ms had an additional feature which worked with the wing flaps through linkage action to reduce their influence when the flaps were lowered. Since they had linkage which could be adjusted on the ground by a mechanic, you could say they were adjustable for trimming the aileron, but only in a manner similar to that done on the fixed tabs of the rudders of the Model 21, early 22, and 32, and not by the pilot while in flight."
