In the times before electronics, mechanical timepieces called marine chronometers were developed to a very high degree of accuracy for use in maritime navigation.
To test the accuracy of such marine chronometers, watchmakers looked to a phalanx of astronomical observatories located in Western Europe to conduct assessments of timepieces.
Watch movements that could compete for accuracy certification at the observatory had typically been specifically built for that purpose alone, they were slow beat movements, oscillating at from 18,000 to 21,600 bph, typically with oversized balance wheels, tweaked and prepared by the best watchmakers often for many years to render ultimate accuracy before they were submitted to the observatory.
In both cases these observatory chronometers were then sold to the public for normal usage as wristwatches, and some examples may still be found today, although they are very rare.
The Girard-Perregaux Calibre 32A movement that went into its Observatory Chronometers heralded a shift in watchmaking technology to higher frequency movements, and thus greater accuracy, that is followed today by watch manufacturers such as Seiko, Patek Philippe, Zenith, Audemars Piguet, Jaeger-LeCoultre, Chopard, Vacheron Constantin, Mathey-Tissot and such.
In recognition of a watchmaking achievement, Girard-Perregaux was granted the Centenary Certificate from the Neuchatel Observatory in 1967, the only time any manufacturer has ever been awarded such.