Quick facts
- Caliber
- 6309(automatic)
- Jewels
- 17
- Beat rate
- 21,600 vph
- Hacking / hand-winding
- No / No
- Water resistance
- WATER RESIST
- Crown
- 4 o’clock
- Production
- 1976–1988
- Modern equivalent
- SRPE93 / SRPK01
Variants
The 7040 and the 7049 differ by market, not by design. Worn & Wound lists the 7049 for North America and the 7040 for Japan and the rest of the world.
| Reference | Market | Day wheel | Status |
|---|---|---|---|
| 6309-7040 | — | — | Pending verification |
| 6309-7049 | — | — | Pending verification |
Serial decoder
Enter the six-character serial from the case back. The 6309 was made from 1976 to 1988, so most serials point to one year; a few point to two.
Possible production date, not a guaranteed date or an authentication. Production date is not the purchase date.
Full decoder with caliber and case codePrice guide
Prices appear after our first sampling of sold listings in November 2026.
| Condition | Low | Median | High |
|---|---|---|---|
A · Collector | — | — | — |
B · Serviced original | — | — | — |
C · Running, unserviced | — | — | — |
D · Project or suspected franken | — | — | — |
Sampled —, n = —, eBay sold listings viewed manually.
Checks before you buy
Replaced parts are common on 6309s. These five checks catch the usual swaps.
Date window The window has a bevelled edge.
A flat-cut window with no bevel is the quickest sign of a replacement dial.
Sources: Worn & Wound; The Watch Site. Our own photo comes with our first shoot.
Dial printing JAPAN 6309-704L T or 6309-704X T with the matching origin text, evenly spaced.
Misspelled origin text such as 'Hong Ko', or a 6 o'clock marker that runs into the bottom printing.
Sources: Worn & Wound; The Watch Site. Our own photo comes with our first shoot.
Hands Flat polished hands, large arrowhead minute hand, seconds hand with a lume dot.
Rounded, thick or raised hands. They can also be later Seiko service parts, so ask.
Sources: Worn & Wound; The Watch Site. Our own photo comes with our first shoot.
Crystal and bezel Flat Hardlex crystal with a frosted edge; black aluminum 60-click bezel insert.
Domed or sapphire crystal, or a red-and-blue insert, without a record of the change.
Sources: Worn & Wound; The Watch Site. Our own photo comes with our first shoot.
Crown and case Unsigned screw-down crown at 4 o'clock that threads in cleanly; crisp edges between brushed and polished surfaces.
A crown that won't screw down, rust around the tube, or rounded edges from heavy polishing.
Sources: Worn & Wound; The Watch Site. Our own photo comes with our first shoot.
Common faults and service
The 6309 is a simple automatic. Check the case as closely as the movement: the crown tube, the gasket seats and the crystal ring.
The mainspring barrel arbor wears its hole in the barrel bridge, a common issue on high-mileage 6309s (Sky Corner; Adventures in Amateur Watch Fettling)
Dried, dirty oil, including on the pawl lever pivot jewels (Adventures in Amateur Watch Fettling)
Damaged crown tube threads
Rust on the gasket seats
A cracked crystal retaining ring
Wear in the mainspring barrel and the rotor bearing
New gaskets alone won't restore water resistance if the crown tube or the seats are damaged (The Watch Site).
Not on Seiko USA's list of calibers not to send (checked 2026-10-26). Seiko USA notes other old calibers not listed may also be returned unrepaired.
Where to look
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How to tell a 6309-7040 from a 6309-7049
Read the case back. The 7049 was made for North America and the 7040 for Japan and the rest of the world, and otherwise the two are the same watch: a 45 mm cushion case, 22 mm lugs, a 60-click bezel and the crown at 4 o’clock.
The dial is less help than you’d think. The printed dial code reads 6309-704 followed by a letter rather than the full case number, so on its own it won’t tell you which of the two you have. The day wheel doesn’t either. The Watch Site’s buying guide records English and Spanish as the most common pairing on these watches, with English and Arabic, German or French also seen. We haven’t found a source that ties any of them to one reference.
Early and late dials
The dial tells you roughly when the watch was made. Earlier dials carry a small Suwa symbol and read JAPAN 6309-704L T along the bottom edge. Later dials read 6309-704X T with MOVT AND DIAL JAPAN CASED HONG KONG. Neither source pins down the month the change happened, so use the serial decoder for the date and the dial only as a cross-check.
Does the 6309 hack or hand-wind?
No to both. The 6309 is a 17-jewel automatic beating at 21,600 vibrations per hour, with a day and date. It doesn’t stop the seconds hand when you pull the crown, and it can’t be wound by hand. If a listing says otherwise, the watch has a different movement or the listing is wrong.
What usually goes wrong, and is a 6309 worth servicing?
Start with the case. Check for damaged crown tube threads, rust on the gasket seats and a cracked crystal retaining ring. The Watch Site also notes wear in the mainspring barrel and the rotor bearing on high-mileage watches. New gaskets alone won’t make the watch water-resistant again if the tube or the seats are damaged.
The 6309 isn’t on Seiko USA’s list of calibers it no longer services, though Seiko USA warns that other old calibers may still be returned unrepaired. Its estimate for mechanical calibers like this one is $359 before tax and shipping. Whether that’s worth it depends on what the watch sells for once serviced, which our price guide will show after sampling.
Is a vintage 6309 Turtle worth buying?
It’s one of the easier vintage Seiko divers to own: plentiful and simple to service. The catch is modification. Replacement dials, hands, crystals and bezel inserts are everywhere, and a watch with all of them can look better than an honest original. Buy the watch with the most original parts you can afford, and use the checks above before you pay.
Where the Turtle sits in Seiko’s diver line
The 6309-7040 and 7049 replaced the 6105 divers in 1976 and stayed in production until 1988. The Watch Site records the 7002 series as the successor. Seiko also used the 6309 movement in other watches, including slimmer dive cases and everyday automatics; this page covers only the cushion-cased 7040 and 7049. Seiko’s current Prospex Turtle, such as the SRPE93, keeps the 45 mm cushion case with a modern movement; our 6309-7040 vs SRP777 comparison sets them side by side.
Sources
- Worn & Wound, Affordable Vintage: Seiko 6309: dimensions, markets, dial codes, crystal, hands, strap, the date-window tell.
- The Watch Site, How to Buy a Seiko 6309 Diver: A Collector’s Buying Guide: day-wheel languages, crown, case back, reprinted dials, faults.
- Mizeni and Caliber Corner: the movement specifications. Seiko USA: service status and estimate.
FAQ
What is the difference between the Seiko 6309-7040 and 6309-7049?
The market. The 7049 was made for North America and the 7040 for Japan and the rest of the world. The case, movement and dial layout are the same.
Does the Seiko 6309 hack or hand-wind?
No. The 6309 is a 17-jewel automatic that doesn't stop the seconds hand when you set the time and can't be wound by hand. It winds from wrist motion only.
What years was the Seiko 6309 Turtle made?
From 1976 to 1988. It replaced the 6105 divers and was followed by the 7002.
How do I know if my 6309 has a replacement dial?
Look at the date window first. An original dial has a bevelled window; a flat-cut window is the most common sign of a replacement. Then check the bottom printing for misspellings such as 'Hong Ko'.
What strap did the 6309 diver come on?
A Seiko GL831 rubber strap. Worn & Wound notes the diver originally came only on that strap.