A Horological Milestone: Advertising from 1966, when GP tried to counter tuningfork-accuracy with their mechanical 39-Jewels Hi-Beat-Gyromatic Caliber.
Ad 2023-07-04: Some asked why this is a horological milestone. Now, while the electric watches since the mid `50s beat no higher and not more accurate than the mechanicals but basically just replaced the manual- or automatic-winding mechanism the upcoming electronic-revolution sparked by the 1961 Bulova Tuningfork-Movements was a completely different story and beat the balance-wheel timed-movements significantly in accuracy.
The reaction of the industry was the race towards higher-beating mechanical movements and this race was won in 1966 by Girard Perregaux with the GyroMatic 32A-movement beating at 36'000A/h. Now, why is this interesting in particular? Because Seiko was close presenting the 5740C movement beating at a similar rate just some months later. And GP proudly announced this victory in a full-page ad in 1966 "Victory of Swiss Watchmaking". A milestone. And especially interesting as it was the precedessor of the next race towards a horological innovation in 1969 / 1970.