Yehoyada then brought out the king’s son, and placed upon him the crown and the insignia. They anointed him and proclaimed him king; they clapped their hands and shouted, “Long live the king!” II KINGS 11:12 (The Israel Bible™)
The Hebrew word used for ‘insignia’ in the verse is aydut (עדות). This term, usually translated as ‘testimony,’ is often used to refer to the tablets on which the Ten Commandments were written and the ark that contained them (see Exodus 32:15 and 26:33). As the Ten Commandments are representative of the entire Torah, Rashi explains that in this verse, the term aydut hints to the fact that the new king is not only given a crown, but also a Torah scroll. This practice is based on the command for a king to write a Torah scroll and have it in his presence at all times (Deuteronomy 17:19). The king must always remember that he is subservient to God, Who is the King of Kings, and is expected to follow His Torah. The Torah is the testimony and insignia of the People of Israel. When they properly observe its laws they are then deserving of Hashem’s promise to possess the Land of Israel.