What do the three numbers and one letter in a production serial number stand for?
They indicate the date of manufacture. We will take the production serial number of 1A02 as an example. "1" indicates the last digit of the year and "A" stands for January. In this manner, "B" stands for February. "02" stands for the day of the month. Consequently, 1A02 represents an item manufactured on January 2, 2001.