Nisemono no tiara
Reinforcing the decoy princess illusion
Act 12 - Sailor V's True Identity was the Princess!
This first appeared in Act 12, when Sailor V showed herself as the Princess.
Even though the Sailor Senshi and the enemy thought the Silver Crystal was set inside it, in Act 20, Sailor Venus revealed that she had multiple fake identical tiaras stored in a case after she activated the fake tiara, after Nephrite seized it, to explode, saying she wasn't planning to give up the real crystal that easy.