Ben Marshall was one of the wealthiest Native Americans living in the Eastern part of Indian Territory (Oklahoma) before the start of the Civil War. He was a trader, farmer, and had large slave holdings. His plantations lay between two rivers and were very productive and Ben was able to accumulate vast wealth.
At the outbreak of the Civil War Ben and a trusted slave loaded four barrels of gold and silver coins onto a farm wagon and drove off into the night to hide the money in a new location. The family soon moved south until after the war had ended.
Only Ben, his wife, and the trusted slave knew the location of the hidden wealth. Each of them died within a few months of each other and with them the secret location of the four barrels of gold and silver coins went to the grave. The Marshall descendants were never able to locate the money.
An old trapper claimed to have found four barrels of money hidden in a cave. On his visits to Ft. Smith he would produce pockets full of gold and silver coins. With some research I think that a person could find the location of the Marshall's land holdings. A good place to start would be 16N 17E sections 32 and 33. A Mr. N. B. Moore saw Ben and his slave the morning after the left to hide the money. I would try and find were he lived as this might give you a direction of travel.
Good luck and good hunting