The Secret of the Ever-Evolving Zenith El Primero

For many watch enthusiasts, the name "El Primero" is synonymous with timeless classics and modern-day classics.
Indeed, its basic design dates back about half a century.
However, what is less known is that Zenith has made various modifications to this movement to improve its performance.
Let's take a look at the improvements Zenith has made that have made this long-selling watch a long-time seller.