UG Hermes "Chronometre"?

In 1936, when this ad was produced, there were no official standards of accuracy or testing for chronometers sold to the public.

Companies sometimes produced movements made to a higher finish, took more care in adjustments and called this their “chronometer” version.

There were competitions among the different companies to see which was the most accurate, but those were specially made and/or adjusted specifically for these competitions.

After WWII, the major Swiss manufactures decided on standards and funded a “Bureau Officiel” to test movements (made by those manufacturers, of course) and issue certifications.

Hope this helps,
gatorcpa