Seiko Presage Open-Heart, Cocktail Time Automatic Dress Watch with 40.5mm Case #SSA358

Seiko Presage Open-Heart, Cocktail Time Automatic Dress Watch with 40.5mm Case #SSA358

The Presage series Seiko SSA358 is powered by the 24-jewel Seiko 4R38 self-winding movement that can also be hand wound and hacked. An open-heart feature at 9:00 on the dial allows you to view the balance wheel in action. The case has a polished (two-tone) finish and a radiant textured silvery-white dial with goldtone hands and hour markers. The two-tone bracelet has a push-button butterfly clasp for quick on and off. A scratch resistant Hardlex crystal is used along with an exhibition back that allows you to view the movement in action. The watch is water resistant to 50 meters.



Diashock
Diashock is a shock-resistance device. When a watch is subject to shock, as when it is dropped on a hard floor, the component most likely to be damaged is the balance-staff pivot, which is the balance wheel’s rotation axis. Even compared to other movement parts, this part is extremely thin, being only between 0.07 to 0.08mm in diameter, or about the same as a human hair. Protection from shock is therefore crucial and the Seiko solution was to create Diashock, a device that absorbs impact on one of the most vulnerable parts of the mechanical watch, the balance-staff pivot. Diashock also reduces friction to ensure optimum amplitude of the balance wheel.
Magic Lever
A Seiko invention in 1959, the Magic Lever greatly increases the winding efficiency of a watch and shortens the time needed for the main spring to become fully wound. This ingenious V-shaped lever allows all the energy generated by the oscillating weight’s motion, whether clockwise or anti-clockwise, to be transferred to the main spring. It is effective, simple and durable and contributes significantly to the longevity of the watch. The Magic Lever system has now been adopted by leading watchmakers throughout the world.
Spron
Utilized in Presage mechanical watches, Spron mainspring and hairspring alloys are exclusive to Seiko watches. Spron features superior elasticity, strength, and corrosion and heat resistance. The Spron family of alloys was originally developed jointly with the Metal Materials Laboratory of Tohoku University and, today, the high performance characteristics of Spron have led to its use in a wide range of fields, from electronics to medicine.