Mechanics 8 min read
How an automatic watch works
Your wrist gives it energy. A spring saves it. A tiny balance sets the rhythm. Follow the journey inside an automatic watch, one pencil drawing at a time.
IWC Schaffhausen · Portofino
Ref. IW391407
The IWC Schaffhausen Portofino Chronograph 39 Stainless Steel / Silver - Blue takes a 20 mm strap: measure between the lugs and that is the only number you need. We list 37 straps in that width. A chronograph carries a bit of sport: perforated leather, rubber or a sailcloth strap all sit well. With a 39 mm case and 30 m of water resistance, a strap of medium thickness keeps the balance. Automatic movement. Most straps here come with quick-release spring bars, so the swap takes a minute and no tool.
Width is a starting point. Check the case and end fittings before choosing.