The 657 is the larger modification of Sinn’s 656 series. This is a pilot’s watch that comes with various useful complications. The timepiece makes use of ETA 2824-2 automatic calibre. It performs 28 800 vibrations per hour and has 25 bearing jewels. One unique feature is the extreme protection from magnetic fields. The watch is also equipped with captive pilot’s bezel with minute ratcheting, pressure resistance, nickel-free case back and scratch-resistant sapphire crystal glass with anti-reflective coating on both sides.