Grand Seiko Spring Drive Shunbun SBGA413G 2026 [Preowned]Overview The SBGA413G "Shunbun" is Grand Seiko's most literal expression of Japanese seasonality in dial form. Named for the vernal equinox, it is titanium cased, Spring Drive powered, and built around a dial that changes character depending on the light it receives. That last quality is the reason this reference exists as a distinct release rather than a colour variant. The 40mm case is high intensity titanium noticeably lighter on the wrist than