The tail wheel assembly carries a component serial number of 3442, which points toward a date of assembly for the airplane of some time in the period of October-December 1941. The number 3442 is the serial number of the tail wheel component, which is known as Part #7500. It is not that 3442 couldn't possibly be the serial number of the aircraft, but it is unlikely to have been. After production has gone on for a while, parts that came together at the assembly building were all mixed up.
Many different components, each with its own serial number, got put together to make one aircraft. Each aircraft, therefore, might have a number of different serial numbers on its various components. The only true aircraft serial number was the one on the main maker's plate in the cockpit, the one included on the painted stencils, and the one recorded in documents, such as status reports, maintenance records, and the airplane's own log books.
A serial number from a component is useful in narrowing down the estimated assembly date of the airplane because some of them were close to the number on the main maker's plate. It mostly was a matter of chance and partly a matter of the manufacturing process. Parts would be made and assembly started on the early planes. At the same time, more parts were being manufactured and stored for the assembly of later planes. If the parts were made by Mitsubishi, each one would have a serial number drawn from a register of serial numbers that used the coding system devised for Mitsubishi. When the final serial number for the whole plane was chosen, it would come from a register just like the one for the components. That's why all of the serial numbers look alike. In an isolated setting, you can't tell a component serial number from an airplane serial number because they look the same. This fact is what has confounded researchers over the years. Salvagers would inspect a wreck, find a component nameplate, see a serial number on it, and think that they had discovered the airplane serial number. But no. It doesn't work that way. Allied technical intelligence officers learned better; they knew how to search for the airplane serial number, not at first, but later. Some of the early official reports on inspections of crashed planes sometimes recorded wrong numbers.
