Flintheart first appeared in the "The Second-richest Duck" (September, 1956).
Scrooge, claiming the title of the "Richest Duck in the World" since at least the 1940s, learns through the press that there is another contender for the title. One owing his fortune to his diamond mines. The rival living in a valley around Limpopo river, South Africa. Or, as the story keeps mentioning, "In the Heart of Africa". He considers that an integral part of his identity is threatened and decides to meet Flintheart and compare their fortunes businessman-to-businessman. His nephews coming along to provide assistance if needed.
Flintheart is introduced as a virtual doppelgänger to Scrooge. They look alike but dress differently. Their main facial difference is that Scrooge has sideburns while Flintheart has a full beard. They both store part of their wealth in giantic Money Bins. Scrooge's has the symbol of an American Dollar on while Flintheart's that of the British Pound. They act alike more than they care to admit as well. Not mentioned by the characters but made obvious by the writer is a big difference in their enviroment. Scrooge is surrounded by Duckburg, a metropolis booming with activity. He is the epicentre of a social network including his family, employees and several enemies. Flintheart lives as a hermit, far away from human habitation. His Money Bin is surrounded by a Savannah and animal life. He has no known family or confidants.
The comparison of their fortunes takes place mostly off-panel but establishes that both control worldwide financial empires of seemingly equal worth. The only thing they have that has not been measured and accounted for are two balls of string, one each. In the belief that nothing should be wasted, they have been collecting lost strings into those balls for years. They decide to decine the winner of their contest on the length of the string. Meaning unravelling miles-long strands of string that would take them from Flintheart's front yard, deep into the African plains.
They hike into the wilderness and the trail turns to have enough dangers and hardships to ensure that victory lies with the rival who protects his own ball of string and his own health while outwitting his opponent. The ruthlessness of the two rivals is established by two mock acts of kindness. An exausted Flintheart is offered a cup of coffee by Scrooge when both teams stop for the night. It was full of sleeping drugs to keep the South African out of action for hours. Before falling asleep, Flintheart found time to advise Scrooge to place his ball of string on the top of a small mound on the trail. To keep it safe from wild animals during the night. Scrooge soon finds out that the mound was a termite colony and that Flintheart had found time to place syrup over Scrooge's string. Resulting it the termites devouring part of the string.
The following day the trail continues and Flintheart finds time to play mindgames with Scrooge. He offers good advise that Scrooge instantly ignores ... to his peril. However various animal encounters gradually reduce both string balls to tiny size. They decide to settle their contest with what was left of their string. They are again equal but unable to admit anyone as their equal. They placed decades-long effort into rising above rivals. Not to accept a rival as an equal. However Scrooge has a flash of inspiration. He places his hand in his pocket and retrieves his Number One Dime, the first coin he ever earned and his charm. Attached to the pocket by string, string which grants him victory. Flintheart faints and has to be carried home by the nephews of his rival.
Flintheart returned for a rematch in "The Money Champ" (September, 1959). This time taking place in Duckburg. However the rules of the contest are different. Flintheart insists they have to liquidate their fortunes into cash and decide based on the area which they can cover with their coins. Scrooge agrees but soon finds out that he enters the contest with a disadvantage. His oil wells, gold mines, and diamond mines throughout the world have suffered acts of sabotage, reducing their worth right at the moment he needed to sell them. His enquiries reveal that Flintheart was behind a systematic campaign against him, using various aliases. Meanwhile two new mountains rise on Duckburg, consisting of piles of coins. As the moment of the contest arrives both rivals feel very insecure at their ability to win. Then a witch doctor offers them both a shrinking juice that could reduce the mountain built by their rival to a tiny ant hill. All he asks as a reward is a meager sum, "five gallons of dollars ". Scrooge is tempted but has a concience and decides against cheating his way to victory. Flintheart jumps at the opportunity and starts attempting to use the juice. Scrooge defends his mountain and no attack actually reaches it. Flintheart looses the contest, having " five gallons of dollars" less than Scrooge. His own insecurity at his ability to prevail in a direct confrontation being his downfall.
Barks last used Flintheart in"So Far and No Safari" (January, 1966).
The two rivals head for an auction in Africa, intending to acquire a supposedky exausted diamond mine. Actually both have scientific reports that the mine still has enough resources. Scrooge and Flintheart pilot their own private jets over the Kalahari Desert, the former accompanied by his nephews. When Flintheart spots his rival's airplane, he reveals that his own has some secrets. It is equiped with machine guns allowing to shoot down enemy plains and also built as a dive bomber, to finish off their crews while they are on the ground. A maneuver Flintheart proceeds to perform. The Ducks manage to escape by placing their clothes on formation of rocks which Glomgold blasts to oblivion. Hoping his enemies are dinner for the jackals. However some of the rocks damage the motor of his jet. He has to crashland not far from where Scrooge and his nephews have found refuge. Both rivals are stranded in the Kalahari.
Huey, Louie and Dewey use their training with animal call whistles to convince several animals to transport them towards the right direction. Flintheart makes his way on foot. They meet each other at the nearest native village. There Scrooge secures the only jeep in the area for himself. Glomgold disguises himself as a witch-doctor and convinces the Ducks to give him a lift to the next village. He offers them some misinformation that leads them to interrupt a religious council in the next village. The Ducks are imprisoned and Flintheart drives away with their jeep. However they soon escape and both rivals arrive at the auction at the same time. The story ends with both rivals biding at the auction while the exausted nephews wait for them to finish.
Barks never reused Flintheart but later writers did. His main weapons remain his intellect and his ability to disguise himself into various roles and fooling his opponents. Apparently the businessman has talent as an actor.