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 7548-700X 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 version of the 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 April of ‘81 is the JDM, 700B variant. Unlike its export counterpart, the “SQ” emblem is absent from the dial. What’s left is a perfect, matte blue black surface with large luminous plots and three lines of text. The hour and minute hands have been carried over from its predecessor, but a black and white reverse “lollipop” with a large pip at the tail end now ticks off the seconds. The bezel rotates smoothly with a firm click in either direction. The “Pepsi” insert shows moderate wear, and just the right amount of color fade from exposure. The case is crisp and unpolished with its factory finishes still quite visible. The crown and case back screw down tightly, and protect the freshly serviced, hacking 7548.  It is completely original aside from a replacement mineral crystal, and is keeping perfect time. We’ve paired it with an updated tropic style strap that makes this one as eye-catching as it is comfortable. Clearly, the secret is out on these early quartz divers, and sourcing clean examples gets more difficult by the day. Don’t wait on this one.

CNS “Tropic” Style Black Rubber Strap

Serviced 4/19/20

Diameter- 42mm

Lugs- 22mm