Australia's oldest Jew, who lived half her life in England and made hats for the Royal Family, will celebrate her 110th birthday next weekend.

But Mary Rothstein's actual birth date is unconfirmed; she doesn't have a birth certificate because her family escaped Russia for London soon after she was born in 1901.

In fact, until this year, her family in Melbourne had celebrated Mrs Rothstein's birthday on February 27 each year because she had told her daughter, Ruth Cavallaro, that she was born on Purim in 1901 and that fell around February 27 more than a century ago.

But earlier this year, Mrs Cavallaro found out the real date for Purim 1901 was March 6.

So next weekend, Mrs Rothstein's daughter, two grandchildren and six great-grandchildren will gather at the nursing home run by Jewish Care in Melbourne to celebrate the milestone.

Mrs Cavallaro visits her mother twice a day, to give her lunch and dinner. "She's never eaten in an ordinary restaurant, only a Jewish restaurant. She's very, very kosher."

Mrs Cavallaro said her mother used to walk to synagogue every Saturday until she was moved into an aged-care facility 17 years ago.

As for her secret to long life, Mrs Rothstein's daughter said: "She's never drunk, never smoked and worked very hard."

Mrs Rothstein is not the oldest Jew in the world, according to Robert Young, a senior researcher at the US-based Gerontology Research Group. "The oldest verified Jewish person is currently Evelyn Kozak of New York City, who was born August 14, 1899," he said.