A long, long time ago, Zenith created a timepiece that was halfway between chronograph and chronometer. Very much a chronometer, because the Espada was a three-hands, simple and accurate watch. And also a little bit a chronograph because its movement was a stripped-down version of their fundamental calibre, El Primero. Here are the facts.
What makes El Primero so special is that it was, back in 1969, the first integrated automatic chronograph movement. Which means it was designed as a whole, as opposed to using a base movement fitted with a functional module, in charge of the chronograph operations. In time, other such movements have appeared, so the only remaining unicity of this movement was its 5 Hz oscillating frequency. For a handful of decades, it remained the only one to beat at 36 000 vibrations per hour. After a while, others managed that too, the most famous of which are the Hi-Beat calibers from Grand Seiko.
In 2012, the brand had decided to use it for another purpose : to power a high frequency timepiece that wasn't a chronograph. And that was the Esapda.
On paper, it was a great idea. But it didn't sell. In 2014, the Espada was morphed into the Synopsis, the same except it had an open heart, which is how Zenith named openings on the dial above the balance wheel, and it had no central hand. It may have been a litlle more Zenith-like in spirit, but it wasn't as beautiful as the Espada and it didn't sell much either anyway. The fact that it had El Primero stamped on the dial was meant to prop it up, but really, it added to the confusion. People thought, as they had been taught, that was the name of a chronograph.
But just exactly how had they managed that watchmaking trick ? Can an integrated movement be disintegrated ? Yes, and litterally so since this move just blew up the project. To make calibre 4650B, Zenith took the core structure of the El Primero and then didn't add everything that makes it a chronograph. Simplified, partially redesigned, it was a 5.58 mm-thick, 30 mm-wide movement with a 50-hour power reserve. And of course it beat at 5 Hz. Whether you're a glass half-full or half-empty kind of person, you can call it non-chronographed or de-chronographed. It even had a silicon anchor, which was a truly rare feature back then. And it had this beautiful, long central seconds' hand reaching to the outer rim of the dial, pointing to a very thin scale allowing the reading of the 10th of a second. 
I must confess that watch really did the trick for me. Not just because of its specs and concept. The Espada was a racing machine in evening wear. It took many cues from the original Espada, launched in the 1970's. But that particular style wasn't the flavor of the day, since everyone was neck-deep in the 1950's and 60's neo-vintage craze. It had rectangular, applied inidices, a great looking, asymetrical date window and a minute track separate from the seconds'. The Espada had tried to make it in a smart, sophisticated way, but it just was the wrong movement and the wrong kind of nostalgia.
