Seiko Slim Turtle 6309

Slim Turtle 6309

In 1982, Seiko introduced the 150m Slim Turtle divers with the automatic caliber 6309 to the export market, the same movement used for the export versions of the Seiko Turtle. In this guide, we will explore the history and features of all the known models in this series.


Introduction to the 6309 divers

The series of automatic 6309 divers started with the Seiko Turtle in 1976.
While the Turtle version for the Japanese market uses the 6306 caliber, the models for the export market are based on the 6309, which has the same structure as the 6306 but with 17 jewels instead of 21, and without the hacking feature.

In 1982, exclusively for the export market, Seiko introduced the Slim Turtle 6309 divers, whose nickname derives from a design slimmed down from the Seiko Turtle, the same design already adopted from 1978 with the quartz Slim Turtle 7548 series, which however differs in the style of the indices.

Seiko Turtle - Slim Turtle

All Slim Turtle 6309 models

The Slim Turtle 6309 divers were produced between 1982 and 1988 in three colors: black, pepsi, and orange.

SDEB37 “Slim Turtle Black”

Case code: 6309-7290
Caliber: Automatic 6309
Year: 1982

Stainless steel case with a diameter of 42 mm and a thickness of 13 mm, Hardlex crystal, screw-down crown, 17 jewels, 47-hour power reserve, 21,600 beats/hour.

To date, no catalog images have emerged, but the following references with their respective dial codes are documented in Seiko materials I have been able to consult.

Case codeReferenceDial codeColorBand
6309-7290SDEB37735MXB19 (6309-735M R)
735NXB19 (6309-735N R)
735LXB19 (6309-735L R)
BlackZLM29 (rubber strap)
Y035S (metal bracelet)
6309-7290SDEI53747PXB19 (6309-747P R)BlackZLM29 (rubber strap)
6309-729ASDEB39735MXL19 (6309-735M R)
735LXL19 (6309-735L R)
PepsiZLM29 (rubber strap)
Y035S (metal bracelet)
6309-729ASDEJ17747PXL19 (6309-747P R)PepsiZLM29 (rubber strap)
6309-729BSDEB41735MXY19 (6309-735M T)
735LXY19 (6309-735L T)
OrangeZLM29 (rubber strap)

Production period

The following table aims to provide an approximation of the production period for the Slim Turtle 6309 divers, based on the serial numbers matched with different case codes.

Some important considerations:

  • the dates are based on the observation of a limited number of serial numbers, and should be considered as purely indicative;
  • the orange configuration (ref. SDEB41, 6309-729B) shows almost all serial numbers from May 1982, with very few exceptions.
Case codeOldest serialsMost recent serials
6309-7290April 1982January 1988
6309-729AMay 1982January 1988
6309-729BMay 1982April 1985

The orange model

The orange model with case code 6309-729B was undoubtedly produced in smaller quantities compared to the other two color variants.
A characteristic that becomes evident from observing the serial numbers is that almost all specimens of 6309-729B are dated May 1982, except for very few exceptions with later serials.

This aspect is interesting considering that the orange variants of the corresponding mid-size and small-size divers of the 4205 series also almost exclusively feature serial numbers from May 1982.

Diver 4205 Orange
Diver mid-size 4205-015A and small-size 4205-014A.

Another aspect shared by the 6309-729B, 4205-015A, and 4205-014A is the black bezel insert with silver lettering.

Specifications of the 6309 movement

Power reserve47 hours
Lift Angle54.5°
Manual windingNo
Hacking featureNo

Technical Information and Parts List