The Amphenol RF 31-5653 is a BNC lockwasher, a stamped phosphor bronze washer with a nickel finish. It is a hardware accessory designed for use with Amphenol BNC jacks — the lockwasher sits between the jack body and the panel nut, providing a spring-loaded grip that resists loosening from vibration or thermal cycling. The silver color is the natural appearance of the nickel plating.
The phosphor bronze body gives the lockwasher its spring temper — it maintains clamping force over repeated tightening cycles without taking a permanent set. The nickel finish provides corrosion resistance in indoor and sheltered outdoor environments, and its conductivity supports the ground path through the BNC shell when the lockwasher is compressed between the jack flange and the panel. This is the same material and finish used across Amphenol RF's standard BNC hardware line.