About 10 years ago, I was really into borosilicate glass and bought a lot of it. (I still can't help but look at it...) I would find it at markets and festivals and buy it right away, ending up with a huge amount... I'm selling some of it little by little. It's made of borosilicate glass, which is melted using a high-temperature oxygen burner. Borosilicate glass is highly transparent and has excellent heat resistance and strength. These are glass Hina dolls (Japanese traditional dolls displayed during the Doll Festival). For the size, please refer to the last photo, which shows them compared to a 500-yen coin.