On first and second photos, they are full denomination of Sao Tome and Principe banknotes that put in circulation since 2018. But there is one denomination missing on the list: 500 dobras (on the third photo), a banknote has dimension of 160×67 mm, same security features as 100 and 200 dobras, and has blue color. Why their central bank omitted the 500 (new) dobra banknote for circulation?