iPhone XS Max Multiple Color Case (Forbidden City Horizontal Inscribed Board By Chinese Empire)

The Hall of Central Harmony (Chinese: 中和殿; pinyin: Zhōng Hé Diàn) is one of the three halls of the Outer Court of the Forbidden City, in Beijing, China, along with the Hall of Supreme Harmony and Hall of Preserving Harmony. It is smaller than the other two halls, and is square in shape. It was used by the Emperor to prepare and rest before and during ceremonies.[1]
The meaning of this Horizontal Inscribed Board is : keep to the center 允执厥中.