The mark consists of a bar graph composed of seven vertical, cube type bars having a three dimensional appearance increasing in height from left to right until reaching the fourth bar at which point the bars decrease in height so that bars five, six and seven are equal in height to bars three, two and one, respectively. The fourth bar (center bar) is the highest. The center bar is shaded and extends horizontally under bars five and six so as to form the letter "L." Superimposed upon the bar graph is a bell-curved line corresponding to the height of each bar along the bar graph. Both the left and right end points of the bell-curved line exceed the base of the bar graph.