In Xi 'an area, what are the silver sachets of the Tang Dynasty mainly used for?

In Xi 'an area, many silver sachets of Tang Dynasty were unearthed, which were mainly used for burning incense. They are round and hollow, divided into upper hemisphere and lower hemisphere. They are fastened by the child's mouth and the mother's mouth, connected by hinges, and equipped with hook chains for easy opening and closing. The lower hemisphere has two concentric rings and a censer connected by a living shaft, and the outer ring is riveted with the ball wall. No matter how the sachet rotates, the incense burner remains horizontal, so that the perfume and incense burner remain horizontal.