The El Primero by Zenith, a famously advanced automatic movement developed in the 1969 and later used to power the Rolex Daytona. Zenith has recently redeveloped the El Primero in their new Defy Xtreme Chronographs. --> Link
Here are a couple of interesting vintage 70s Zenith El Primero Chronos including the monstrous sized model shown above. via HeuerBoy --> Link
And the tonneau cased Zenith El Primero below with burgundy-to-red gradation dial & overlapping registers.
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