I don't see much difference between Graves lead hand grip per their website 'Advanced Grip Instruction' photos and IMA. The photos show a club in the hand vs a narrow rod so their might be some room for various interpretations but I see the same reference to the muscle I mehtioned and a contact with the same point at the first joint of the index finger. Viewed from the other side there is an apx 20 deg angel between the line of the knuckles and the club. Pretty much the same.
NG, on the other hand, has taught a number of lead hand grips in its history. Some matched IMA (after all Scott was the first director of instruction for NG
) and some didn't.
Peter