Why is the yuan on the "one hundred yuan" a "circle" and not a "yuan"?

The "circle" originated from the silver circle, because the silver circle is round, and a silver circle is called one yuan. Later, because yuan characters are more convenient to write than round characters, everyone wrote yuan, which is actually a white character. However, because of its wide use, dictionaries were later forced to admit it. Therefore, the authenticity should also be "round". Circle is the standard usage when the amount is capitalized, but it is usually more suitable to use yuan in business. Both yuan and circle are applicable. Circle is used when the amount is capitalized, but yuan is usually more suitable for business. For example, the capital of RMB 5 12.00 is Wu Bai twenty yuan only. This is the most formal writing. The circle can also be changed into yuan, and the whole can also be changed into positive.