Durante o confronto entre Malfoy e Dumbledore, pouco antes da morte deste, no final de Half-Blood Prince , eles discutiram como Malfoy estava se comunicando com Madame Rosmerta:
Tell me, how have you been communicating with Rosmerta? I thought we
had all methods of communication in and out of the school monitored.”
“Enchanted coins,” said Malfoy, as though he was compelled to keep
talking, though his wand hand was shaking badly. “I had one and she
had the other and I could send her messages —”
“Isn’t that the secret method of communication the group that called
themselves Dumbledore’s Army used last year?” asked Dumbledore. His
voice was light and conversational, but Harry saw him slip an inch
lower down the wall as he said it.
“Yeah, I got the idea from them,” said Malfoy, with a twisted smile.
Aparentemente, tanto Dumbledore quanto Malfoy estavam cientes do método secreto de comunicação da promotoria. Como eles descobriram isso?
Embora seja possível que Dumbledore soubesse da existência do DA porque a reunião original no Hog's Head foi ouvida (como argumentado nas respostas a esta questão ), o método de moeda de comunicação não foi introduzido até a quarta reunião , que não foi escutado, como documentado no Capítulo 19 da Ordem da Fênix (minha ênfase):
Hermione soon devised a very clever method of communicating the time
and date of the next meeting to all the members in case they needed
to change it at short notice, because it would look so suspicious if
people from different Houses were seen crossing the Great Hall to talk
to each other too often. She gave each of the members of the D.A. a
fake Galleon (Ron became very excited when he saw the basket at first,
convinced that she was actually giving out gold).
“You see the numerals around the edge of the coins?” Hermione said,
holding one up for examination at the end of their fourth meeting. The
coin gleamed fat and yellow in the light from the torches. “On real
Galleons that’s just a serial number referring to the goblin who cast
the coin. On these fake coins, though, the numbers will change to
reflect the time and date of the next meeting. The coins will grow
hot when the date changes, so if you’re carrying them in a pocket
you’ll be able to feel them. We take one each, and when Harry sets the
date of the next meeting he’ll change the numbers on his coin, and
because I’ve put a Protean Charm on them, they’ll all change to mimic
his.”
É improvável que eles descobriram através da traição de Marietta, porque Umbridge disse que Marietta parou de falar logo depois de mencionar que haveria uma reunião naquela noite:
“Oh, very well, you silly girl, I’ll tell him,” snapped Umbridge. She
hitched her sickly smile back onto her face and said, “Well,
Minister, Miss Edgecombe here came to my office shortly after dinner
this evening and told me she had something she wanted to tell me. She
said that if I proceeded to a secret room on the seventh floor,
sometimes known as the Room of Requirement, I would find out
something to my advantage. I questioned her a little further and she
admitted that there was to be some kind of meeting there.
Unfortunately at that point this hex,” she waved impatiently at
Marietta’s concealed face, “came into operation and upon catching
sight of her face in my mirror the girl became too distressed to tell
me any more.”
(É possível que Marietta tenha mencionado isso mais cedo na conversa, mas esse não parece ser o tipo de informação que seria a primeira coisa sobre a qual falar.)
Além disso, durante todo o confronto no escritório de Dumbledore, Umbridge não mencionou esse método de comunicação.
Então, para reiterar, como Dumbledore e Malfoy chegaram a conhecer o método de comunicação da moeda?