Cro WatchesSeiko 6309 guide: the movement behind the Turtle and the Seiko 5
Updated 12 October 2026 · Cro Watches, Vilnius
The 6309 is one of Seiko's great workhorse movements. It powered the legendary 6309-7040 "Turtle" diver, but most 6309s were everyday Seiko 5s with colourful dials, built in the late 1970s and 1980s.
6309 at a glance
| Type | Automatic, day-date |
|---|---|
| Jewels | 17 (export versions); a 21-jewel sister, the 6319, was also made |
| Beat rate | 21,600 beats per hour (6 ticks a second) |
| Power reserve | about 40–45 hours |
| Hand-winding / hacking | No / no |
| Era | late 1970s to late 1980s |
| Related | 6319 (21 jewels), 6349 (23 jewels, often in dress and square cases) |
The 6309-7040 "Turtle"
The most famous 6309 is the 6309-7040 diver, nicknamed the Turtle for its wide cushion-shaped case. Made from the mid-1970s to the late 1980s, it is now a collector's watch: original examples typically sell for €300–700 in Europe, and Seiko has re-issued the design in modern form. Originality matters a lot on Turtles, so check the dial, bezel insert and hands carefully.
6309 Seiko 5 references
Far more common are 6309 Seiko 5s: round, cushion and square cases with sunburst dials in blue, green, salmon, grey and turquoise. You'll see references such as 6309-8230, 6309-8900, 6309-5710, 6309-6240 and 6309-7320 (a square dress case). They are affordable, tough and look great on a steel bracelet.
How to set a 6309
6309 watches come with two different calendar systems depending on the version: some change the day by pressing the crown, others have a quickset in the middle crown position. Our day and date guide shows how to tell which one you have.
Common issues
- Replacement dials: many 6309 cases today carry a 7009 dial. Look at the code at 6 o'clock: if it starts with 7009, the dial isn't original to the case. Fine for wearing, worth less to collectors.
- Worn crowns and stems: easy and cheap to replace.
- Tired calendar: a day that hangs halfway usually means the watch needs cleaning and oiling.
Is a 6309 a good buy?
Yes. Parts are plentiful, any watchmaker can service it, and a good 6309 Seiko 5 sells for about €60–130 in Europe. It is a proper 1980s mechanical watch for the price of a modern fashion watch.