The Grand Seiko Standard is a Seiko-exclusive accuracy standard for mechanical watches which has been established to ensure superior performance of Grand Seiko mechanical watches irrespective of the differences in environmental conditions in which a watch is used. "Grand Seiko Standard Inspection," which measures gain / loss (daily rate) under various environments, is carried out at the manufacturing plant for 17 days in total, and only mechanical watches that satisfy the standard are given the title of "Grand Seiko."
The Grand Seiko Standard differs from the other recognised chronometer standards in two important respects. While most accuracy standard testing is done for five positions at two temperatures, the Grand Seiko Standard tests six positions at three temperatures. This is because the Grand Seiko Standard seeks to replicate real world conditions. The sixth position, namely the 12 o’clock upright position, is the way many people place their watch when not wearing it. In addition, the extra temperature rating is closer to body temperature. The idea is simple - to test the watch under conditions similar to actual use.
* Inspection of the movement for the Grand Seiko Standard Inspection Certificate is made prior to casing. Movement performance is carefully measured in the static position under scientifically controlled conditions.
* The accuracy of the watch may vary depending on the actual usage conditions and may differ from the certified accuracy.