Dumbledore's Army Coins
Brilliant Room of Requirement
Hermione Granger's Desk, Ministry of Magic
Created by Hermione Granger as a way to discreetly communicate with members of Dumbledore's Army, these fake galleons were linked by a Protean Charm to reflect changes made to the master coin. The numerals engraved around the edge conveyed the time and date of the next Dumbledore's Army meeting and the coin would heat to indicate the change. Many members of Dumbledore's Army are said to retain their coins to this day and carry them with pride.