Our wrist watches had springs then
The youngsters now may not be able to imagine it. Their hair may spring up on hearing that. Yes the wrist watches we were wearing in our young days had springs inside them. While today everyone have the smart watches, it is very difficult to even think of such mechanical watches with springs, wheels and gears . Yes it is fact, historical fact.The most vital and vulnerable part, rather the beating heart of those watches was a unique part called hair spring. It is also known as balance spring.
This was the vital part because it oscillated in a prescribed resonance frequency, which in turn controlled the various toothed wheels attached to the balance wheel and made the watch/time piece needles(clock hands) move at the precision of second, minutes and hours. Thus the hair spring and the balance wheel were the most vital parts or actual regulating parts or the heart of those time mechanical watches and time-pieces and clocks.
The watch doctor or watch repairer had to be more accurate and skilled (than today's medical surgeons)to repair and put back the hair spring and balance wheel back in its correct place and act.
I had a never forgettable memory of spoiling my grandfather's cherished wrist watch by trying to show my 'engineering skills' in meddling with the hair spring inside it.
To those who had not seen the hairspring and inside of a mechanical wrist watch, I would request to go to an old watch repair shop or antiques museum and se it. It is worth that.