Bovet's hairsprings – a secret formula

The hairspring is both the heart and brain of a mechanical watch movement. Bovet's manufacturing facilities, the Dimier 1738 Manufacture, is one of the very few companies on Earth that actually manufacture them. That number is so small the hairspring remains a secret thing. First and foremost, no one knows what it is actually made of, with the exception of maybe three or four people within Bovet.