Dumbledore's Army coin

The Dumbledore's Army Coin was an enchanted Galleon created by Hermione Granger in 1995 to inform members of Dumbledore's Army when the next meeting would take place. Hermione enchanted normal coins using the Protean Charm. Around the edge of each coin was a series of numerals which represented a serial number belonging to the Goblin that cast the coin. The Protean Charm allowed these numerals to change into the time and date of the next meeting of the DA whenever the master coin, owned by Harry Potter, was changed. The coin would also warm up to alert the holder to the change.

In 1998, Neville Longbottom used the coins to summon former members of Dumbledore's Army to Hogwarts School of Witchcraft and Wizardry to fight the Death Eaters and reclaim the school. The former members alerted many others, including the Order of the Phoenix, and set the scene for the Battle of Hogwarts.

In later years, the surviving members of Dumbledore's Army would keep their coins, regarding them as badges of honour.

Appearances

 * Harry Potter and the Order of the Phoenix
 * Harry Potter and the Half-Blood Prince
 * Harry Potter and the Deathly Hallows