If you look at the digits from the last one from the right, it is the actual sequence number that are the amount of scanners produced and are 4-5 digits. Then to the left are one or two zeros and to the left of them are the date code. I think the right one only goes up to 8 as the highest so might relate to half quartely, 45 day periods. The next digit to the left are the last digit of the year. The rest to the digits at the start of the serial# are model type and manufacturing plant numbers.
That's how I interpret how the serial# are built up.