This tuning fork vibrates at 528 Hz, a frequency close to C5 as played on a piano in standard tuning. But it’s intended for use to repair your DNA, which, as you imagine, is not something a tuning fork can accomplish. (There are several “sacred frequencies,” all reputed to accomplish various medical effects. And, of course, you can buy a set of tuning forks to cover all of them.)
There’s also a music CD that plays the 528 Hz tone, also intended to repair your DNA.
If you don’t yet think this is a deep pool of insanity, you should read the description, if not the text, of “The Book of 528: Prosperity Key Of Love,” an insane 528 Hz-based book written by a dentist.