Seiko's 6138 was the sophomore release to the 6139 and added a few features lacking on the former. In addition to a rolling 12 hour register for the chronograph, it could now be manually wound at the crown, and the day and date could be quick set independently. With enough design variations to suit nearly every taste, adding one to any collection is an easy decision. Adding this one however, is much easier said than done. The 7000 is easily one of the rarest and most sought after 6138s available. This one from March of ‘73 is the first of it’s kind that we’ve ever had the privilege to offer, and it isn’t for a lack of trying. Of those available on the market, many are drenched in aftermarket parts, and are in less than desirable condition. To have found an example that is as well preserved as this one was an opportunity we weren’t going to pass up. It’s “Calculator” moniker refers to the slide rule double bezel that can be used to complete any number of mathematical equations on the fly. Exactly how that’s done, could be better answered by someone else, but I can tell you that it looks awesome. In addition to the outer rotating bezel is a clear sliding cursor that can be used in tandem with the slide rule function. Moving inward, the dial is the nicest example we’ve seen. The matte black surface is free of staining or blemishes, and the original luminous material has developed an even and clean, creamy patina. The sub registers are finished in charcoal gray and exhibit a subtle sunburst effect. The hands have no paint chipping or loss, and the luminous is uniform throughout. The chronograph hands are a vivid yellow, and offer a nice contrast to the dial and sub registers. The case is unpolished, and the original circular brush finish is still intact. The coin edge bezel rotates smoothly in either direction, and the slide rule inserts are the originals, neither of which shows anything but the slightest wear. As the original plastic cursor was no longer attached, I made the decision to install the best possible alternative, and tracked down an East Tech 1:1 replacement. The 6138B is keeping near perfect time post service, and the chronograph functions are smooth and responsive. We’ve paired it with a two-piece desert tan RAF NATO that perfectly complements the dial and hands, and provides a comfortable fit and finish. Don’t miss this opportunity, as we won’t likely be able to repeat it anytime soon. 

Clockwork Synergy Desert Tan Two-Piece Double Layer RAF NATO (clockworksynergy.com)

Serviced 9/25/18

Diameter- 44mm

Lugs- 19mm