Washington (CNN) President Donald Trump loves to talk about the quality of Trump golf courses, buildings and even water.

Financial documents released by Trump's former lawyer Michael Cohen during his testimony before the House Committee on Oversight and Reform Wednesday show Trump, in 2013, put a financial value on the brand: $4 billion.

The number appears in a document that, according to Cohen, was used to demonstrate Trump's net worth to Forbes magazine as well as to bankers and insurers.

There are no additional details on the statement Cohen provided to Congress about how the "brand value" was determined or why it appeared so suddenly. And brand value, traditionally, is almost impossible to quantify.

"It is a very elusive thing," says Robert Passikoff, president of the brand consultancy Brand Keys, who'd tracked the Trump brand for the past 30 years. "I don't think there's ever been an accurate internal accounting of the value of his brand."

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