This is a dunhill silver key holder. It's an item I'm holding for someone. To use it, firmly pull down on the protrusion at the bottom. It will open with a click. See the second photo. To close it, pull the protrusion again, and the top protrusion will be pulled down, allowing it to close. I couldn't take a photo of closing it while doing it myself. Diameter: 3.9 mm Material: Silver Retail Price: 40,000 yen Thank you.