Their king’s crown - The word rendered their king (Malcham) is also the name of the national idol of the Ammonites (Jeremiah 49:1, Jeremiah 49:3 margin; Amos 1:15; Zephaniah 1:5). Moreover, the weight of the crown, which is calculated to be equal to 100 or 125 pounds weight, is far too great for a man to wear. On the whole, it seems most probable that the idol Malcam is here meant.
Related Commentaries of 2 Samuel 12:30
2 Samuel 12:30
30 And he took their king's crown from off his head, the weight whereof was a talent of gold with the precious stones: and it was set on David's head. And he brought forth the spoil of the city in greatf abundance.