5-10 K Process:
(1)    In 1976, FDA said they had to be notified of every device marketed.  They listed every device in the federal register.  They classified all those devices in existence into classes I and II.  The company had to submit a document as to whether the device was safe as a class III.  All such products were grand-fathered in.
(2)    After 1976, every device has been classified.  But some devices made today are the equivalent of a device used before 1976 which was grand-fathered in.  If it is the same as grand-fathered in device, then you can apply for a 510(k) for exemption and approval.
(3)    Rarely used for Class III and usually for Class II devices.