Cal. 3020CS is a time-only hand-winding movement with central seconds from Naoya Hida & Co. based on the ETA 7750 ebauche. Hida’s second movement, Cal. 3020CS uses the Cal. 7750 main plate, barrel, wheel train, and escapement with a custom 3/4 plate and balance cock. The automatic winding system is removed, replaced by a custom click for hand winding, and the chronograph and date complications are removed.
A wheel is added to the back of the movement for central seconds, adding 0.7 mm thickness compared to the small seconds Cal. 3019SS. This wheel is covered by a plate screwed to the main 3/4 plate, as visible in the photo at right. This plate includes three visible jewels including a large one at center, and an indentation, likely for a pivot. The movement presumably leverages the unused central chronograph seconds hand as indirect running seconds.
Instead of the traditional Valjoux or Triovis fine index system, Hida’s movements use the simpler Etachron system. This includes a mobile stud carrier and regulating arm with rotating blocks to effectively shorten or lengthen the hairspring.
Cal. 3020CS was introduced with the Naoya Hida Type 2A in 2020. It has been used in the following Naoya Hida watches:
- 2020 NH Type 2A (10 sold)
- 2021 NH Type 2B (10 sold)
- 2022 NH Type 2C (10 sold)
- 2022 NH Type 2C-1 (10 sold)
The NH Cal. 30 Family
All three Hida movements to date have a similar appearance, and all are based on the 7750 ebauche, wheel train, barrel, balance, and escapement. The small seconds and moon phase movements likely share the same balance bridge and plate, and both feature 18 jewels.
The central seconds hand on Cal. 3020CS is driven using a rear-mounted wheel, requiring a secondary plate at the center. It also features four extra jewels, for a total of 22.
Cal. 3021LU, used in the Type 3, uses the moon phase mechanism from ETA’s Cal. 7751 but omits a seconds display entirely. Like Cal. 7751, the moon phase indicator is adjusted with the crown in position 2.