When Seiko decided to pursue development of their first core quartz diver, they didn’t have to look far for inspiration. In fact, the 6309 had only been in production for two years when the first 7548’s rolled off the production line in 1978. Bearing more than a passing resemblance to the 6309-7290, the 7548-7000 shares an almost identical case, and the bezel, insert, crown, crystal retaining ring, and crystal are all interchangeable between both styles. And if architectural similarities were all there were, it would no doubt be a great watch by default. However, Seiko did as Seiko does, and quite literally built a quartz driven 6309 movement. With the case back removed, one look tells you all you need to know about early Seiko quartz movements. They were not plastic disposable machines to be quickly swapped out at the first sign of trouble, but beautifully, if not overly, engineered movements with jeweled pivots and precisely machined plates. Removing the dial and hands reveals a calendar and keyless works that could easily be mistaken for a 6309. Rather than cousins, these two calibres are brothers. One battery driven, and one spring driven; each as capable as they are impressive. This example from December of 1983 is the North American export variant denoted by the SQ designation on the dial. The dial is perfect in matte black with large luminous plots that have taken on a light cream patina. The hour and minute hands are instantly recognizable, however, this set has naturally oxidized to an almost completely black finish. The luminous is the original with some sinking through the middle and a matching patina to the hour plots. In order to prevent crumbling, I applied a bonding agent to the reverse side of the hands for support. Counting the seconds is a black and white reverse “lollipop” with a large pip at the end of the tail. The bezel rotates smoothly with a firm click in either direction, and the insert, showing little wear, has begun to develop a deep blue color from exposure. Aside from a replacement crystal, it’s completely original and the case is crisp and unpolished with its factory finishes and bevels still clearly visible. The crown and case back both screw down tightly with ample threading for a tight seal. Still a bit under the radar, these early quartz divers are a somewhat available, budget friendly option to add some Seiko diving history to your roster, but as we’ve discovered, the secret is out.

CNS Rally “Tropic” Style Black Rubber Strap

Serviced 4/2/21

Diameter- 42mm

Lugs- 22mm