How to interpret numbers found on SEIKOs

Foreword regarding Orient numbers
Previously and obviously incorrect, Orient was also mentioned on this page to follow SEIKO's "nomenclatura". As Dan aka Zeb - a fellow PMWFer - is still investigating, most Orient watches use a 46943 movement and for Orient watches, the number on the rotor denominates the watch caliber. Dan is still collecting information and I will update this page once his project is finished.

How to interpret the various numbers on SEIKO dials and case backs
A good rule with no exception (known to me) is to check the little printing at 6 o'clock.

From the Dial at 6 o'clock you can read the Caliber for almost all Seiko/Orient Models:

A0 = The number in a box (next to 7010 in this case) is an information for the repair personnel on how to open and close the watch case. The letter "A0" or "F" which is also popular, could well be the number for the SEIKO case opener to use. This information is from Manel, Spain and he received it from Seiko Spain. Here is the original text in Spanish. Thank you Manel. Manel had inquired about a SEIKO 5 which had the letter "F" in a box on the case back.

La letra “F” en el fondo de la caja significa el modo de construcción de la caja para que sepan los relojeros cómo se monta y desmonta el reloj.

From the Back read the Manufacturing Date out of the Serial Number for almost all Seiko Models:

1 N 0 0 9 8

1 stands for the year, 1991 in this case most likely, you will have to guess the decade!

N stands for November according to the following notation for the 2nd digit:

1 = Jan
2 = Feb
etc.
S = Sep
O = Oct
N = Nov
D = Dec

..0098
the running number of that model

6F24 - 7010 A A0: 6F24 is the movement number, 7010 A A0 is the case reference number. A0 obviously also seems to be some sort of a reference number, if you know what it means, I would be more then happy to receive your email!

Japan A, Made in Japan, the letter "A" stands for the location of the SEIKO factory. Obviously locations "A", "D", "G" or "S" exist*.

*Adriano (thank you for the hint!) from Brazil told me he got information from Seiko that the following locations exist: "A", "D", "G" or "S". However Seiko did not tell him what letter stood for which location. If you know what locations the letters represent, please mail me. Thank you.

The "Ax" letter I believe stands for the case size.

"A0" is 41mm case

....

"A4" is 36mm

and so on

Nick

CA. USA

7S26A on the Rotor of Automatic numbers also denominates the Caliber
The "A" is the version of that caliber. It can be "B" or even "C". They are revisions and improvements of the first "A" model. Similar to ETA's 2824, 2824-1, 2824-2.

Example
The 6119 is another example. Calibers 6119A, 6119B and 6119C exist. 6119C has a bilingual day and an instant day and date change (push of crown) while the A and B versions are date versions only. Again thank you Adriano for this information!

Note:
It is normal that the number on the dial e.g. 6F24-701L R 3 is different from the number on back e.g. 6F24-7010 because the after dash numbers are the dial reference number and case reference number respectively. However the movement or caliber number e.g. 6F24 should always be the same on the dial and on the case back. Otherwise you might have watch in your hand that has been puzzled together. You might observe that especially on flea markets where normally a lot of "Frankenwatches" are sold (leaned from Dr. Frankenstein's attempt to puzzle together different human parts and create a new human being).