For decade itself, you have to know the actual production dates of the movement itself. For month, 1-9 are Jan thru Sep, with 'O' for Oct, 'N' for Nov, and 'D' for Dec. Then look at 2nd digit/letter to tell month. General rule for manufacture month/year is to look at 1st digit of serial # to say what year within decade.

Usually the case style or the introduction dates of the movement can help to narrow this down though. You have to know the age of the watch to the nearest decade so sometimes it can be a little bit difficult. And O,N and D for October, November and December).For example if the serial number was 864825 and you knew the watch was made sometime in the 1970's it would indicate it to be made in June 1978. The first number represents the year and the second number (or letter) represents the month (1-9 for Jan.-Sept. Seiko Watches - How to date your watch by the serial number Seikos have the date of manufacture written into the serial number which is engraved on the back of the watch also the movement-model numbers are also engraved onto the case back. Enter the number into the 'Model No' search box at the top of the screen. Visit the Citizen website (see Resources). If you know the serial number of a Citizen watch, you can find the watch on Citizen's website.Well, Zenith serial number 1204675 is shown in a cut in a 1909 ad.Do you think that the number is: a) Based upon a watch built long before the ad appeared?.

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