[Researcher]

From the "Blue Ink" catalog --

E - 10-gauge, Damascus barrel, pistol grip, $85
F - 10-gauge, Damascus barrel, straight grip, $80
G - 12-, 14-, 16- or 20-gauge, Damascus barrel, pistol grip, $80
F - 12-, 14-, 16, or 20-gauge, Damascus barrel, straight grip, $75

R - 10-gauge, Twist barrel, pistol grip, $60
S - 10-gauge, Twist barrel, straight grip, $55
T - 12-, 14-, 16- or 20-gauge, Twist barrel, pistol grip, $55
U - 12-, 14-, 16, or 20-gauge, Twist barrel, straight grip, $50

For D on up, grip choice and 10-gauge are all the same price as 12-, 14-, 16- or 20-gauge