Por este foro, hay gente que sabe mucho de SEIKO, y te podrían precisar con mas exactitud, pero por si te puede servir de guía:
Deciphering the serial number
- The first digit signifies the year the watch was made. It doesn’t tell you the decade – only the year. This will present a problem because you may not be able to distinguish whether the watch was made in 1997 or 2007. The digits always range from 0 to 9.
- The second digit denotes the production month. Seiko uses 1-9 for January to September. October is represented by the number 0 (zero, not the letter "O") while November and December are abbreviated to "N" and "D" respectively.
- The remaining 4 digits represent the production number of the watch in a sequence. It is generally believed that the first watch produced every month begins with "0000" and the last watch made in that month ends with "9999". Going by this convention, up to 10,000 watches of a particular model could be manufactured in one month. The sequence number is reset for the following month. Therefore if Seiko made up to 4,900 pieces in February, the last watch produced will have the the sequence number 4900. For the following month of March, the first watch produced will have the sequence number 0000 instead of 4901.
The following table below gives examples on how the serial numbers are interpreted:
<table width="489" border="1" cellpadding="2" cellspacing="0"><tbody><tr><td valign="top" width="93" align="center">
Caliber</td><td valign="top" width="107" align="center">
Serial Number</td><td valign="top" width="68" align="center">
Year</td><td valign="top" width="106" align="center">
Month</td><td valign="top" width="113" align="center">
Watch Number</td></tr><tr><td valign="top" width="93" align="center">
7S26A</td><td valign="top" width="107" align="center">
717872</td><td valign="top" width="68" align="center">
1997</td><td valign="top" width="106" align="center">
January</td><td valign="top" width="113" align="center">
7872</td></tr><tr><td valign="top" width="93" align="center">
7T32</td><td valign="top" width="107" align="center">
8N1030</td><td valign="top" width="68" align="center">
1998</td><td valign="top" width="106" align="center">
November</td><td valign="top" width="113" align="center">
1030</td></tr><tr><td valign="top" width="93" align="center">
6105</td><td valign="top" width="107" align="center">
200421</td><td valign="top" width="68" align="center">
1972</td><td valign="top" width="106" align="center">
October</td><td valign="top" width="113" align="center">
421</td></tr><tr><td valign="top" width="93" align="center">
6138</td><td valign="top" width="107" align="center">
731999</td><td valign="top" width="68" align="center">
1977</td><td valign="top" width="106" align="center">
March</td><td valign="top" width="113" align="center">
1999</td></tr><tr><td valign="top" width="93" align="center">
6309</td><td valign="top" width="107" align="center">
4D8001</td><td valign="top" width="68" align="center">
1984</td><td valign="top" width="106" align="center">
December</td><td valign="top" width="113" align="center">
8001</td></tr><tr><td valign="top" width="93" align="center">
8L35</td><td valign="top" width="107" align="center">
259393</td><td valign="top" width="68" align="center">
2002</td><td valign="top" width="106" align="center">
May</td><td valign="top" width="113" align="center">
9393</td></tr><tr><td valign="top" width="93" align="center">
7S26B</td><td valign="top" width="107" align="center">
760023</td><td valign="top" width="68" align="center">
2007</td><td valign="top" width="106" align="center">
June</td><td valign="top" width="113" align="center">
23</td></tr></tbody></table>
Los 6309 se fabricaron de 1976 a 1988 así que;
según esta tabla, y asumiendo el nº de serie como 806629, el reloj sería de octubre de 1978 o del 88 aunque parece mas lógico del 78 por el tipo de reloj.