The Zenith El Primero debuted in 1969 as one of the world's first automatic chronographs. Zenith featured the new movement in a number of different case shapes at launch, but there is nothing quite like the model we have here. This reference came a few years after the El Primero was released in the early/mid 1970s, and it would be produced until around the end of that decade. Collectors today refer to this model as the "TV" or "Big Blue" due to its squarish-tonneau case shape that resembled a television set and the distinct blue colored dial.

This watch features a large stainless-steel case with a beautiful blue dial that has a tachymeter scale around its periphery, adding some nice depth. The bezel is polished, so that contrasts nicely with the brushed case and bracelet. The dial has three sub-dials with "TV" shaped silver rings that accentuate the case design. The watch also has an integrated stainless steel bracelet that starts at 31mm wide at the lugs and tapers to 16mm at the clasp, adding a nice level of comfort on the wrist. Zenith used two different bracelets for this model. The earlier examples, like we have here, had a thicker, heavy style of bracelet, but eventually Zenith switched to a lighter one made by Novavit SA (NSA). The story goes that the initial bracelets Zenith used for this model were made by Châtelain. The company went out of business in the middle of this model's production, so Zenith switched to bracelets made by NSA. The bracelet is dual signed at the clasp with both the Zenith and Châtelain logos.

The chronograph pusher is also interesting on this model. When viewing from behind, you'll notice there is a single piece of steel that functions like a lever when engaging with the pushers. This innovation was supposed to allow for easier use of the pushers, especially compared to a traditional design. It adds to the watch's unique vintage style.