Purchased at the Ikebukuro Tobu Department Store 20 years ago and stored after being used a few times. There is a small black stain on the back, as shown in the second photo. It's an older model without an engraving on the back. The diameter is about 4 centimeters, as shown in the eighth photo. I can add more photos, so please comment if you have any questions. A storage bag is also included.