The 350 introduced a frequency of 32,768Hz, with an advertised accuracy within about 0.164 seconds per day. This accuracy blew its competition out of the water and set the frequency standard for decades.
The information provided to me by Girard-Perregaux about this movement is as follows:
“[This] Model [is] from 1971. [It was the] First watch with the quartz oscillating at 32,768 Hz, a frequency adopted since then as a universal standard.
The GP-350 movement was equipped with an integrated circuit produced by Motorola, bringing together the equivalent of 300 transistors within an area equivalent to 5 mm2. Its consumption was reduced to 4 micro-amperes, enabling sufficient battery life. This was the first time that quartz wristwatches passed the static and dynamic tests (impacts, magnetism, temperatures) at the Neuchatel Observatory. After 38 days of tests, the GP quartz watches certified by Neuchâtel Observatory for the year 1971-1972 had proven their extraordinary accuracy and their reliability.”