John Mayer’s first signature Martin guitar, the OM-28JM Limited Edition, was released in 2003 in a run of 404 guitars (representing an Atlanta area code). And in 2006, Martin released the OMJM John Mayer, which has become a staple of the Martin line. Those were the first two guitars in what has become a 20-year relationship with the superstar guitarist and songwriter, and Martin has now collaborated on five unique John Mayer models.

Recently, Mayer sent one of his OM-28JM guitars in for repair, and this fascinating video shows talented Martin craftspeople re-fretting the guitar, sanding the fretboard, fitting a new nut, re-fitting the bridge, and more. At the end of the video, the guitar is tuned up and fingerpicked, ready to go back to its rightful owner.