The 6138-7000 – known as the “Calculator” – is one of the most unique 6138 chronographs available. It features a double external bezel, one rotating and one fixed, to carry out a host of mathematical calculations. Although made completely obsolete by digital calculators, performing these calculation mechanically is quite amusing. Those familiar with using a slide rule should be able to utilize the 6138-7000’s bezels with little effort. This is a variation of Seiko's twin register chronograph that you don't see that often.very unusual in as much as it has a slide rule bezel and indicator much like the contemporary Breitling navitimer.Great condition and well looked after for a vintage watch that was made in the early 1970's Made in Japan - 21 Jewels - Seiko 6138B automatic movement The overall condition of the watch is excellent Few external signs of wear are to be seen Assess the condition with the pictures provided for a better idea. Black dial - good condition. Keeping good time,the deviation on the test machine shows +/- "0" seconds per 24 hours All chrono function works as it should. Solid Stainless Steel case recently buffed and polished Diameter without the original crown is 45mm Aftermarket Seiko signed stainless steel bracelet,dial and bezel. Original Seiko box. The watch hands is aftermarket. Total bracelet length including case 21 cm. The watch will be shipped via TNT, UPS or DHL to worldwide with a tracking code. Delivery time is only a few days* for Europe and approx. 5-7 days* for other countries. Speedy delivery for gift. Please, be aware of customs duty. Buyer is responsible for import VAT and taxes if necessary. *Estimated business days