from the internet...
...the person portrayed is my great-great grandmother. James Barton Longacre was the chief engraver of the U. S. Mint in Philadelphia and was competing in 1835 for a design for the planned copper cent. Knowing that several Indians and their chief (I understand it was Sitting Bull but am not certain) were to be shown the Mint as part of their visit to the Great White Chief in Washington, his (Longacre's) daughter, Sarah, begged to be brought to the office to see the exotic Indians.
"The old chief was intrigued by the 12-year-old with her flaming red hair, removed his war bonnet and placed it on her head. Her father did a quick sketch of the moment to show his wife. Later, pressed for an entry for the contest, he refined the profile of his Pennsylvania Dutch daughter wearing the Indian headdress and won by one vote. Sarah was much teased in the city for a time. The initial, which can be found in early mintings at the end of her jaw line, refers to her name, Sarah Longacre.