A counter balance is a control surface that extends past the pivot line... I'll post some pics tonight if no one else has any for a sig SE.

Simple explanation is basically a piece of wood on top of the rudder that lines up with the horizontal stabilizer's leading edge in front, and even with the rudder's trailing edge in the back. (can also be done with the elevator, and probably the ailerons if you really want to, might be interesting to see the results!)