The PRE-2015 system doesn't apply to early ESP's, some of which had no serial number tracking system at all and used random numbers. For this we apologize, and we are working to maintain a more consistent system going forward. you may still come across the occasional serial number that may conflict with, or doesn't fall under any of the listed categories. This has resulted in alot of confusion, and. ESP Guitar Company says: 'Unfortunately the factories at ESP Japan have not kept a consistent and sensible serial number tracking system in place over the years. I keep record of this data in order to try to deduce other correspondences. Tapped means that the F500T was a beefed-up pick-up with almost twice as much windings than a standard Fender pick-up, but it had a tap after the normal number of windings, so you could switch off the second half of the coil so to say. For old guitars we can only know the exact data reading the ESP warranty card (when there is), or unscrewing the neck (if the neck is bolt on) and read under it becuse probably theres the data write on pencil). Here David Schecter came in with the invention of the F500T pick-up, the first successful tapped pick-up. Many records have been lost during years and most of all were destroyed in a fire accident on late '90s in ESP Japan factory. Unfortunally ESP didn't keep good records of old serial numbers.