Zenith Chronomaster Open — The Open Heart That Beats at 36,000 VpH   Zenith Chronomaster Open Review: Why the El Primero 3604 Still Matters In a market crowded with skeletonized dials and openworked everything, the Zenith Chronomaster Open stands apart for a reason that has nothing to do with aesthetics. It's the only 39.5mm chronograph in its class that lets you watch a...