This miniature portrait of an unknown lady is signed "B Coolidge" for Bertha Coolidge (1880-1953) who worked in New York and Boston.
There were several people named Bertha Coolidge, but she is thought to be the Bertha Coolidge born in Lynn MA on Aug 28, 1880, the elder daughter of a Boston merchant Albert Leighton Coolidge (16 Jun 1832-<1900) and his wife Elizabeth E Wiggin (Oct 1851-?) who were married on 20 Aug 1879 in Boston when Albert was aged 47.
There is a book "Kate Douglas Wiggin As Her Sister Knew Her" by Nora Archibald Smith, which has a miniature of Kate Douglas Wiggin by Bertha Coolidge as a frontispiece. Presumably Kate was related to Bertha's mother. Kate Douglas Wiggin was a noted author who lead the kindergarten education movement in the United States. She also wrote children's books including "Rebecca of Sunnybrook Farm" (1903).
It seems likely Elizabeth was Albert's second wife as there is also a record of Albert L Coolidge marrying Mary A Buttrick in Boston on 16 Jan 1856. Bertha made many trans-Atlantic crossings, the earliest at age 5 with her parents, but more after World War I. Perhaps it was a way to mix and attract potential new clients.
There are references to Coolidge's exhibited work at AMERICANS AT BIG SALON.; Unusually Large Number of Paintings by ... and at Exhibition of Miniatures at the Academy; ART AT HOME AND ABROAD and there are miniatures by her in the Metropolitan Museum and MFA Boston.
The MFA collection in Boston includes a miniature portrait of Bertha Coolidge painted in 1911 by Laura Coombs Hills, see Bertha Coolidge 573