I'll be damned! He's got Scrugg's tuners, or something similar, on his guitar which is why he can be so precise with his pitches when de-tuning and retuning.
EDIT: AH! Keith tuners.
The headstock is non-unique, except for the Scruggs style banjo. Bill Keith at the Beacon Banjo Company in Woodstock, NY, USA makes these. They allow Legg to change tunings quickly between or during songs.
On the rear side of each tuner are two tiny thumb wheels that allow the tuner to be tuned and de-tuned to a fixed position. On the headstocks front side are six levers that pull the strings to a tighter or looser position.