I don't know which part you are disagreeing with , Chuck , but some more "commercial" examples of which I speak. WW1 , Colt , could not provide 1917 revolvers in numerical order by serial number , had to be stamped with a second number ( the service number) and go by that to do so. ( I have never figured that out).
Carbines--lots of commercial carbine manufacturers did not use all the numbers in thier assigned blocks and did not assemble in order in thier blocks. Some did not even use thier blocks in order , and at least once one used part of one block , then used all of a second , then returned to the first block.
Several times one manufacturer would run short of a part and have some transfered from another manufacturer ( including recievers). These parts had to of came from a stash they had to pull from to send ( otherwise they would have then been out.
Garands--I remember something about the WIN-13 Winchesters , and I remember someting simular with either H&R or INT.
Now , in this particular case , the bbls were marked with the date WHEN MADE. It was stamped with the serial number WHEN MATED to that reciever. In between , the bbls were in storage and were pulled when needed. They did not spend the time to make sure all the January bbls were used before going on to Feburary's , nor did they throw the January bbls away when they were dragged out because they were already using March's bbls. , they just used them.
This is why you have to make educated guesses on some guns you find. The books may say there is a small problem , but the gun looks right as far as finish and wear. New info is comming to light all the time and a LOT of what we KNEW to be fact a few years ago we now know is not always the case because new exceptions have been found.
Chris