The logo of the Bank of China resembles the ancient coin with the word 中(Middle) which is the name of China.
The ancient coin is in a circular shape with a square in the middle, representing the heaven or the sky surrounding the earth. According to Bagua, the shape for Qian gua (heaven) is circle and the shape for gold is also circle; the shape for Kun gua (earth) is square. (Please refer to page 22 for detailed explanations on Later Heaven Bagua) in my book http://www.penangfengshui.com/index.php?pages=book_enjoyyourlife_ebook
It also resembles the important principle of the Yi-jing or I-Ching i.e. 天人地 heaven (sky), people (human) and the earth (land). It means the world is formed by the human who step on the earth which sky on top of us.