A55 is the center. He approaches the ball, leans down and puts his right hand on the ball as the rest of the linemen come up to the line. A12, the QB, calls "SET" and all of the offensive linemen go down into a 3 point stance. At the same time that they do so, A55 puts his left fist on the ground right next to the ball, in the Neutral Zone. Is this encroachment on the offense?

I have nothing.

The snapper can have parts of his body (everything except his feet) in the neutral zone but no part of his body other than the hand on the ball may be beyond the foremost point of the ball.

NF 7-1-1