Dakota,
what the heck this has already strayed WAY off course so I will keep going
. Also as an Engineer, if the device is calibrated at the required interval, determined by manufacturer and department (usually less time then previous, but if justified why longer it can be approved) and the device is still within its calibaration period then this practice should pass an audit. The tuning fork verification is just that a feel good, unofficial comparitive reference method to enable the departement to know if there is a reason to decrease the calibration interval on a certain device. Some could even use this as a "verify before use" type of calibration if the tuning fork was calibrated and tracable to NIST. not a recommended practice but could be done.