Between 1971 and 1973, IWC produced watches with tuning fork movements.
These are movements without a pendulum, the resonator used is a tuning fork. Therefore, no ticking but a buzzing is audible when holding the watch next to the ear.
The oscillations are maintained by means of an electronic maintenance circuit containing a transistor.
Apart from a contact between the base and the transmitter, which is used to set the time of the watch and for storage purposes, the movement has no electrical contacts.
The tuning fork functions not only as a resonator but also as a motor.
As IWC‘s management didn’t want to take the risk of investing a lot of money in this new technology, they decided to buy the movements from Ebauches SA which produced them under license from Bulova from Biel. IWC used two different movements:
- Caliber 150 with date only (ESA 9162)
- Caliber 160 with day and date (ESA 9164)
Here is my Reference 3470:
Inside is the movement caliber 150 with 300 Hertz which makes the seconds hand move very smoothly and continuously. My watch is very precise as it gains only one second per day.
IWC was right in not investing too much money into this technology as very quickly tuning fork movements were substituted by the even more precise and more durable Quartz Movements.
I was lucky as my watch came with box and papers:
A great personal extra for me: the date on the warranty from the purchase is in the month after my birth!
Philipp
