Fin was an Australian tennis company. Fin's claim to fame was their Vibration Control system (VFS), where the throat had a gap between the two center main strings. When a throat grommet was jammed into the gap, it was supposed to dampen nearly all the vibration traveling down the frame. It remains to be seen if this technology did indeed work, however, since it's not around anymore.
Fin's VFS or Vibration Free System can be found on the bridge of the racquet and almost completely eliminates vibration. The Fin was a recommended racquet for those with arm problems due to its extremely comfortable response.