The color appearance of Nickel-plated and stainless steel is relatively indifference, so need to distinguish through the multimeter, adjusted the multimeter to the diode gear, the two pens moved on the metal dome at the same time, if the sound is continuous and crisp, it is nickel-plated, if it’s intermitten, then the surface is stainless steel.
The material is gold plated, silver plated, and phosphor bronze, which can be distinguished by appearance, gold plating is usually single plated, contact surface is gold. Silver plated is usually single side silver plated, contact surface is silver. And phosphor bronze is silver plated, the surface is copper, the contact surface is silver.
