Seiko’s automatic 701x series – including this full serviced 7015-6010 Time Sonar automatic chronograph here, on its original Seiko bracelet – arrived to the market two years later than Seiko’s famed 6139 series, with both featuring a similar single-register 30-minute layout and day/date complication.
However, the two movements shared no components, and the 701x had its own rather unique feature - certain models, like the one here, were signed “Time-Sonar” on the dial and were the first automatic chronographs available with display backs, a rarity for any watch at the time.
Although similar to the 6139 series, the 701x series was arguably the more technically advanced of the chronograph movements. The 7015 has an additional flyback functionality (which allows the user to immediately restart the chronograph without having to first stop and reset, akin to the popular vintage Citizen 8110 bullhead).
Of note, the 701x series was the thinnest vertical clutch column wheel chronograph during a portion of the 1970’s, existing from 1970 through ’77. The movement has a diameter of approximately 27mm and is only an astounding 6.4mm tall, which is significantly thinner than the 6139. Finally, the 701x line had some of the most attractive variations of any early Seiko chronographs, including the square cased 7016-5001 “Seiko Monaco.”
This Time Sonar comes on its original Seiko stainless-steel bracelet, and with nylon strap, rugged travel case, and springbar tool.
1970's Seiko 7015-6010 Time Sonar Automatic Chronograph
DIAL: Seiko-signed transparent dial with correct minute and hour hands. It also features a virbrantly-colored green chrono hand and 12 o’clock marker (these came in three colors: yellow, red, and a funky green). Date and day function - with Kanji Japanese and English day variants - at 3 o'clock positions work as designed.
CASE: 38mm x 43mm stainless steel case, with correct tinted see-thru caseback.
CRYSTAL: Hardlex crystal, no scratches.
BAND: This 7015 comes on its original Seiko stainless-steel bracelet, which will fit slightly over an eight-inch wrist - it also comes with a black nylon strap.
MOVEMENT: Seiko 7015 flyback automatic movement. We have performed a full service on this watch.
CROWN: Recessed unsigned stainless-steel crown.