What distinguished the Omega Speedmaster during NASA's initial qualification process in the early 1960s?

Answer

It was the only commercially available model to successfully pass the exhaustive stress tests.

NASA acquired several commercially available watches, but the Omega Speedmaster emerged as the sole reference to successfully pass the entire battery of stress tests required for flight certification.

What distinguished the Omega Speedmaster during NASA's initial qualification process in the early 1960s?
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