The Seiko/TMI/SII caliber NH35 is a hand-windable, hacking upgrade from the Seiko caliber NH25. It is one of the world’s most popular automatic movements and is widely available in many affordable/microbrand watches.
In the technical documentation, Time Module claims that the NH35A accuracy range is within -20~+40 seconds per day under normal conditions. They recorded these accuracy measurements without the date complication being active. This shouldn’t have any noticeable bearing on the accuracy, but it’s interesting nonetheless.
Note: When you attempt to get a measurement of your watch’s accuracy, it’s important to make sure your watch is fully wound or the lack of power reserve may skew the test results. TMI states that measurements should be done within 10-60 minutes after the movement is fully wound up.
Winding the Mainspring
So what does fully wound up mean? The NH35A should be fully wound after about 55 manual turns of the crown.
NH35A Also Known As…
It’s also important to note that the Seiko NH35 movement is basically an unbranded version of the Seiko caliber 4R35. for example, the NH36 is an unbranded version of the 4R36 (day + date) found in the Next Generation Orange Monster. More information here.
Crown Position Functions:
0 (against the case): Clockwise = Manual Winding / Counterclockwise = Nothing
1 (pulled out one click): Clockwise = nothing / Counterclockwise = Date setting
2 (pulled out two clicks): Time setting clockwise and counterclockwise