The Columbia Dispatch posts this article by Ralph and Terry Kovel about how seeing “Royal Bonn 1755″ marked on Bonn pottery does not mean it was created in 1755:
The 1755 date refers to an earlier pottery in Bonn. Royal was a word that added prestige and helped to sell dishes, so many companies used it. In England the right to use the word usually meant the company had sold something to the royal family.
In other countries, consent from royalty wasn’t needed. Royal Bonn ceramics included porcelain and earthenware.