Which component, invented around 1675 by Huygens and Hooke, provided spring-driven devices with an accuracy approaching pendulum clocks?

Answer

The balance spring (hairspring)

The balance spring, working with a balance wheel to create a harmonic oscillator, allowed spring-driven clocks and watches to achieve accuracy approaching that of perfected pendulum clocks.

Which component, invented around 1675 by Huygens and Hooke, provided spring-driven devices with an accuracy approaching pendulum clocks?
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