“Book Descriptions: It was small, slim, about the length of her hand; the leather cover was soft, the sewn-in binding was crisp, and the thick vellum pages were empty. 'Tom Marvolo Riddle' was printed in ancient, flaking gold leaf across the front.
He had been a Slytherin, a prefect, and head boy in 1944.
She had checked.
[ ALTERNATIVELY - Hermione finds Tom Riddle's diary, but not everything is different. ]