Shanghai in Chinese is two characters: 上海. It is frequently abbreviated to single character, 上, as mint identification.
Shenyang is two characters: 沈阳, and it is frequently abbreviated to single character, 沈, for mint identification.
Shenzhen Guobao is four characters: 深圳国宝. On the PCGS slab it is shorten to Shenzhen: 深圳. However, the character Guo, 国 is frequently used for its mint identification.