Seiko Caliber, Reference, and Serial Numbers

Calibre, reference and serial numbers Since we are still waiting for the delivery of our Seikos, now is the time to talk about a very important subject: the watch numbers. Again, while we're focusing here on Seiko watches, there are similarities with other brands so please pay attention. There are 4 lots of numbers which are important for proper identification.  1. The first number is the movement caliber:

This number can be found on the watch mechanism itself. Here, it is engraved on the rotor bridge: 6119 C. The letter after numbers indicates version (A, B, C etc) Calibre number is essential when ordering MOVEMENT parts.

2. The second number is dial reference number:

It is located ON THE WATCH DIAL underneath the 6 o'clock position. Very fine print, you need an eye glass to read it. This one is 6119-6020S. What does it mean? During the watch production, each movement can be fitted with practically an unlimited number of dials. Black, white, silver, gold, different height, day/date or date only etc. And each dial would have corresponding calendar wheels and set of hands. Therefore 6119-6020S means that dial set is 6020 S style (black dial, silver hands with luminous material, silver hour markers etc) and it is married to movement calibre 6119. This number is essential for ordering dial parts.

3. Watch model reference number (red) is located on the case back:

Again, it starts with the calibre number followed by the case style number: 6119-6023 The case style describes the physical case properties:
steel, gold, gold plated, dimension, water resistance, type of winding crown, bracelet, crystal, bezel and many other external components. However some components are both movement and case related - like the stem.

4. The fourth number is the watch serial number (green). It is located on the case back (for solid metal backs) or printed on the glass (for see-through case backs). It is usually a 6 digit number.

My watch is no. 4D3410. The first digit on the case back represents the LAST digit of manufacturing year decade. If you know the decade of production (70s, 80s, 90s) then you can figure out when your watch was manufactured. The second number/letter is the month. 1=Jan 2=Feb etc 9=Sept 0= Oct *note this is 0 not letter O N=Nov and D=Dec So my watch was produced in December ???4. As you can see, the number alone is not sufficient to determine the actuall age of the watch (unless you have a new-ish one) but based on the movement calibre and style, I would guess that most likely it was made in December 1974. The rest of the digits present is actually the serial number 3410. It was a #3410 of reference [6119-6023] produced in month of December. Finally the letter F (yellow) is country code - while the case back is stamped JAPAN the watch could still have been produced in Seiko's overseas factory. Obviously, it is absolutely crucial to know the calibre, dial number and model reference number when referring to your watch or when ordering spare parts. It is always a good idea to quote ALL numbers to your spare parts supplier: "I need [this part] for Seiko caliber 6119 C (note C!) dial number 6119-6020S and case number 6119-6023."


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