Understanding Seiko Serial Numbers
How do you find out how old a seiko is by serial numbers?
The serial number indicates the last digit of the year and month made in the formay YMxxxx(x) where months go 1-9,O,N,D so a 8N1234 would be Nov.
Jan - 1.
Feb - 2.
Mar - 3.
Apr - 4.
May - 5.
Jun - 6.
Jul - 7.
Aug - 8.
Sep - 9.
Oct - 0.
Nov - N.
Dec - D.
To narrow down the decade you might judge by the case number. One tip for guessing decade is if the serial is 7 digit, it was probably made '67 or earlier whereas 6 digits would be '68 or later. (late '67 / early '68 transition to 6 digit serial numbers).
The following image shows a typical model number, case code and serial number.
In this case the serial number is 640607. This means the watch was made in 1976 (the first 6) in April (the number 4). Of course the year could be 66, 86, 96 or even 2006. This is where knowing the different model and case styles helps!
The marking also confirms the model number as 0124 with a case type of 0049