Now I understand. There are no indicators on the sideplates of this I-Grade gun, only the large screw heads toward the rear of the plates. Chambers, by the way, appear to be 2 3/4". I see no marks except the serial number on the underside of the barrels, so I assume the only way to figure out the chokes is to gauge the muzzles or pattern the gun. McIntosh says the barrels were taper-bored from breech to muzzle rather than choked near the muzzle.