Pat Broderick original Batman art before he was famous

In the late 1970s my grandfather went to the commodore before they demolished it and slvaged any items he could. He came across this drawing by Pat Broderick. After some research I found that in 1973 Pat Broderick entered a marvel competition for a chance at becoming the next marvel artist. He wound up winning the competition. It would seem as though this was one of the drawings used by Broderick in the competition. What would a fair value be on such a rare and unique piece. Any input is much appreciated.