The Classic "Turtle" - the 6309-7040

The 6309 represents a line of dive watches produced by Seiko from 1976 to 1988. They are sandwiched between the 6105 line and the 7002 line, and perhaps best known for popularizing the "Turtle"-style cushion case. The cushion case first came out with the 6105-8110/8119 and by the time the 7002 rolled out in 1988, Seiko divers have adopted the familiar slim case we still have today in the contemporary SKX007/009.

Note that late 2015/early 2016 sees the reissuance of the cushion case via the SRP773/775/777/779, so in a sense what we are seeing is Seiko's design aesthetic going full circle.

The 6309 line is powered by a 17 jewel automatic movement with day/date which neither hacks or handwinds. Power reserve is around 45 hours fully wound.

Case diameter is 44mm excluding the crown, lug-to-lug length is 46mm. Case thickness is 14mm, and lug width is 22mm. In an era when the typical men's watch was less than 40mm in diameter, this was considered huge at the time. 44mm nowadays is pretty much par for the course.

Water resistance is 150m, 50m short of modern day dive watch standards. I wouldn't recommend diving or even swimming with one now, unless the seals have been renewed and the watch pressure tested.

This particular sample in my collection is all original despite being more than thirty years old (date of manufacture per serial number is July 1984). The only replacement component is the relatively current Seiko Jubilee-style stainless steel bracelet, which is to be expected since this watch was originally supplied with a rubber strap, which has long gone.  

Some photos: