Greenberg released audio recordings of the conversations, including with "Barron", that he said he had recently discovered when going back through his notes from the time.
He told Greenberg that Trump was worth far more than $200m Forbes had estimated previously and had become a billionaire after his father, Fred, had handed over most of his assets to his son. "'You have down Fred Trump [as half owner]. but I think you can really use Donald Trump now.' Trump, through this sockpuppet, was telling me he owned 'in excess of 90 percent" of his family's business.
Jonathan Greenberg claims Trump called him in 1984, pretending to be an official from the Trump Organization.
Despite doubting some of Trump's claims, Greenberg said that it took several years to prove Trump's false statements on his finances and that he was not as rich as he said he was.
Greenberg said Trump's actual net worth at the time as a real estate developer was less than $5 million, though the magazine had listed it as $100 million for its first-ever Forbes 400 list. Following the report, Trump denied it was him on the phone or that it sounded like him in an interview with NBC's "Today" show.
Greenberg goes on to allege that Trump widely overstated his net worth, by 20 times what the magazine had him pegged for.
The journalist recorded his conversations with Barron and noted that he was "amazed" that he didn't "see through the "ruse" that he was speaking with Trump". "We were so wrong". "It eventually paved a path toward the presidency".
"Barron's" aim was to get Trump placed higher up the annual Forbes rich list. Greenberg added that Trump was the one person most obsessed with his standing on the list in its history.
"When I first contacted him for the inaugural issue, Trump pulled out all the stops to convince me that he was the wealthiest real estate developer in New York", Greenberg claims in the op-ed. Trump wasn't just poorer than he said he was.
Greenberg broke the news in a Washington Post story. The magazine instead published that Trump and his father Fred Trump were worth $200 million each.
Trump, however, did climb the Forbes listings, and has been listed in the magazine since the mid-1990s.
"John Barron" was only one of Trump's tactics, routinely sending his confrontational lawyer Roy Cohn to distort his business deals and holdings to anyone expressing doubt.
Greenberger wrote in the Post that he made a decision to publish the off-the-record conversation because the "intent to deceive" released him from his "good-faith pledge".