The words “king of Judah,” belong to Coniah, and prove that he was king regnant when the prophet wrote. The prophet gives him the name by which he was known when in a private station 1 Chronicles 3:16 as he had done previously with Jehoahaz. These two kings bore their royal names for so short a time that they probably never got into general use.
The signet - The badge of office. To part with it, was to part with the royal authority.