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Sylvia Bloom, a legal secretary who worked at the same firm for nearly seven decades, lived a modest life in Brooklyn, riding the subway to work most days.

But unbeknownst to her friends and family, she was a closet millionaire. The frugal secretary, who died in 2016, quietly amassed a fortune of more than $9 million through a string of savvy investments, according to The New York Times.

In her will, she left $6.24 million to the Henry Street Settlement, a local social services group, along with another $2 million split between Hunter College and a scholarship fund.

Bloom is far from the first person to discreetly cultivate riches while living a life of apparent thrift. Here's a look at some other secret millionaire philanthropists whose company she has joined.

The janitor with a knack for picking stocks

Ronald Read, a former gas station attendant and janitor who died in June 2014, was known as a private and penny-wise man. He wore faded flannel shirts and drove a used Toyota Yaris.

It was only after his death that his shocked hometown of Brattleboro, Vermont learned that he had an $8 million nest egg. He left most of the money to a local library and hospital.

Ronald Read, a former gas station employee and janitor, died in June 2014 at age 92. Estate of Ronald Read via AP

Read had a talent for identifying promising stocks: "Investing and cutting wood, he was good at both of them," his lawyer, Laurie Rowell, told Reuters in early 2015.

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He was so humble in appearance that somebody once paid his bill at his favorite coffee shop because they assumed he could not cover it, Rowell said.

The librarian who saved nearly every penny he earned

Robert Morin, who spent almost half a century working as a librarian at the University of New Hampshire library after graduating from the school, lived alone and ate Fritos for breakfast.

And so when he died in 2015 at 77, former colleagues and acquaintances were surprised he had bequeathed his entire estate of $4 million to his alma mater, according to the Boston Globe.

Robert Morin bequeathed the University of New Hampshire his entire estate of $4 million. University of New Hampshire

Morin, who tucked away nearly all his earnings in checking and retirement accounts, was a mild-mannered eccentric who rarely bought new clothes.

"He was somebody you only meet once in a lifetime," his financial adviser, Edward Mullen, told the Globe.

The secretary whose $180 stock purchase grew to millions

Grace Groner, a secretary who scooped up clothes at garage sales and lived in a spartan one-bedroom house in Lake Forest, Illinois, survived the Great Depression.

That harrowing experience might explain her thriftiness. But she was also generous: Groner gifted an estate worth $7 million to Lake Forrest College, her alma mater, after her death at 100 in 2010.

Where did she get all that money? It all stemmed from a $180 stock purchase she made all the way back in 1935, according to the Chicago Tribune.

"She could have lived in any house in Lake Forest," William Marlatt, her attorney and friend, told the Tribune. "But she chose not to."

The flight attendant who lived on peanut butter and ice cream

Doris Schwartz lived like a "bag lady," one her friends told the York Daily Record.

She was a former flight attendant and onetime teacher who seemed to survive on peanut butter and ice cream, spending her twilight years in a crowded row house in West York, Pennsylvania.

But when Schwartz died at 93 in 2013, she left $3.4 million to a local community foundation to help teachers and students, according to the Daily Record.

"To apply her own personal education to create a legacy that lives forever for others," Bryan Tate, the vice president of the foundation, told the newspaper. "What a grand and exciting way to be remembered."