Seiko NH39A

Seiko Instruments (TMI) · Automatic · Entry tier · Family: Seiko NH3x

NH3x-family automatic with an open-heart aperture over the balance at 9 o'clock and a small 24-hour indicator subdial (at about 10:30); no date. TMI describes it as "Three Hands with 1 Eye, Small 24 Hour Indicator Hand", the 24-hour hand being synchronised with the regular hour hand (a day/night indicator, not an independently set GMT), so `functions` lists only hours, minutes, seconds and the open heart. TMI spec sheet (rev. 16.11.2022): 12 lignes, Ø27.40mm (Ø29.36mm with the dial holding spacer), 5.32mm high, 24 jewels, 21,600 vph, duration "more than 41 hours", accuracy -20 to +40 s/day (23 ±2 °C), manual winding, ball-bearing automatic winding in both directions, second hand stop mechanism (hacking), antimagnetic ≥4800 A/m; rotor marked JAPAN or MALAYSIA by country of origin. TMI's casing notes say a screw-type case back is required and that the caliber is "non-corresponding with diver's watch". Trade version of Seiko's 4R39 (Grail Watch Reference gives 40h for the Seiko-branded 4R39).

Watches with the Seiko NH39A

Watch	Price from	Movement	Dia. mm	Thick mm	Crystal	Micro-adjust
Cadisen C8168	$150	Seiko NH39A	42	12.5	Sapphire	—
Pagani Design PD-1674	$152	Seiko NH39A	44	15	Sapphire	no bracelet
Pagani Design PD-1736	$190	Seiko NH39A	43	13	Sapphire	—
Pagani Design PD-YS015	$203	Seiko NH39A	41	13	Sapphire	no bracelet
Pagani Design PD-YS010	$247	Seiko NH39A	50	13.5	Sapphire	no bracelet

Sources

• Time Module (TMI), NH39A watch movement specification and drawing (rev. 16.11.2022)
• Grail Watch Reference, Seiko 4R39 (open heart at 9, 24-hour subdial at 10:30; offered by TMI as NH39A)