Irving Kahn, the Manhattan money manager whose astounding longevity enabled him to carry firsthand lessons from the Great Depression well into the 21st century, has died. He was 109.

He died on Feb. 24 at his apartment in Manhattan, his grandson, Andrew Kahn, said Thursday.

A studious, patient investor from a family whose durability drew the attention of scientists, Kahn was co-founder and chairman of Kahn Brothers Group Inc., a broker-dealer and investment adviser with about $1 billion under management.

Last year, at 108, he was still working three days a week, commuting one mile from his Upper East Side apartment to the firm’s midtown office. There, he shared his thoughts on investment positions with his son, Thomas Kahn, the firm’s president, and grandson Andrew, vice president and research analyst. The cold New York City winter kept Kahn away from the office the past several months, his grandson said.

“I prefer to be slow and steady,” Kahn said in a 2014 interview with the U.K. Telegraph. “I study companies and think about what they might return over, say, four or five years. If a stock goes down, I have time to weather the storm, maybe buy more at the lower price. If my arguments for the investment haven’t changed, then I should like the stock even more when it goes down.”

Staying Sharp

Kahn worked to stay mentally agile, reading three newspapers daily and watching C-SPAN, according to a 2011 article in New York magazine.

Among the memories he filed away was his work with Benjamin Graham, the stock picker and Columbia Business School professor whose belief in value investing influenced a generation of traders including Warren Buffett. Graham, who died in 1976, distinguished between investors, to whom he addressed his advice, with mere “speculators.”

Kahn assisted Graham and his co-author, David Dodd, in the research for “Security Analysis,” their seminal work on finding undervalued stocks and bonds, which was first published in 1934. In the book’s second edition, published in 1940, the authors credited Kahn for guiding a study on the significance of a stock’s relative price and earnings.

Graham Eclipsed