Like a gemstone? No, it's a magic prop!...PREMIUM METAL Series.
Movie is PM GOLDEN KEY GOLDEN COMBINATION(M7148). We highly recommend purchasing both "PM SHOCKING KEY" and "PM IMPOSSIBLE KEY & RING"(M7145).
The golden key (90mm in length) has a protruding part at the tip. With just a light press from your fingertip, the protrusion begins to slide smoothly along the body of the key, eventually moving all the way to the base. The spectator clearly sees the entire movement of the protrusion in real time. Afterward, the key is handed to the spectator to examine, and they confirm that the protrusion is securely fixed at the base and does not budge.
The combination with the identical-looking "PM IMPOSSIBLE KEY & RING" successfully eliminates any possibility of a switch, using mental misdirection to ensure the illusion is flawless.