Order of the Phoenix Ch. 23:
“And Dumbledore — what about Molly?” said Professor McGonagall, pausing at the door. “That will be a job for Fawkes when he has finished keeping a lookout for anybody approaching,” said Dumbledore. “But she may already know . . . that excellent clock of hers . . .” Harry knew Dumbledore was referring to the clock that told, not the time, but the whereabouts and conditions of the various Weasley family members, and with a pang he thought that Mr. Weasley’s hand must, even now, be pointing at “mortal peril.”
How did Dumbledore know about the clock?
Was Dumbledore ever at the Weasleys' house before the events of book 6?