A/N: Just another headcanon thingie. The next chapter might be quite a bit sexier...we'll see if I can get over my embarrassment long enough to write it!
In the Fire Nation, the rules concerning the usage of royal seals were convoluted at best, and virtually incomprehensible at worst. There was, for example, a difference between the seal used by the heir to the throne, and those used by other male children of the Fire Lord, and those used by other female children of the Fire Lord. There was also a distinction between the seal type used by blood royalty versus those used for royalty by marriage. And this was just for the immediate royal family…the guidelines for more distant relatives were best not discussed at all.
Each type had a basic outline, but the details were individually customized. Each member of the immediate royal family would be assigned one of these customized designs at some point, usually by the age of twelve (although there were exceptions, such as when young children inherited the throne). The cadet branches had to make do with just generic designs. And woe to anyone who used the wrong one! It was considered a huge scandal, and courtiers who had nothing better to do would hash over the ramifications for weeks.
Of course, some people just didn't care. After Prince Zuko's banishment, Princess Azula was known to use his seal whenever she could get away with it. During the time between the Phoenix King's departure and Sozin's Comet, she also ordered her father's seal to be brought to her room. No one was brave enough to tell her to wait until after the coronation, when a new Fire Lord seal would be made just for her. It was said that she stayed up the whole night, melting wax onto paper and pressing the seal onto it, over and over and over again…