To my astonishment, the thing had an authentic look.
Perhaps some unbelievable guest would arrive, a person infinitely rare and to be marvelled at, some authentically radiant young girl who with one fresh glance at Gatsby, one moment of magical encounter, would blot out those five years of unwavering devotion.
There are no more uses of "authentic" in the book.
Show samples from other sources
I appealed to Boney now, Detective Rhonda Boney with the sympathetic air that seemed at least partly authentic.