The ability to keep a stable rate over time is probably the most important quality of a watch. A stable watch is predictable and can thus be easily regulated.
Shown above are the 12 Hour Test results for three
popular Seiko movements. Note that the error scale has been set to ±30 S/D in relative mode for easier
comparison. The actual error value is ignored.
1. An old 7S36 movement, probably in need of servicing. This would be nearly impossible to regulate.
2. A brand new 4R36 movement. With much less fluctuations and long periods of stability, this might be a good candidate for the Relative Regulation method.
3. A factory-adjusted 9S85 Hi-Beat movement. Less than one second rate drift for the 12-hour period — almost a straight line on the ±30 S/D scale! [ See the same test on ±5 S/D scale. ]