A rare survivor from the late 18th century – the Grace Growden Galloway memorial brooch (complete with a lock of her hair) being offered for sale by Charterhouse in Sherborne, Dorset on November 11, together with a ring, at a joint estimate of £600-1000.

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The objects concerned, a brooch and a ring, are both items of Georgian mourning jewellery. Worked in gold and set with seed pearls, the brooch contains locks of hair from Grace Growden Galloway, a heroine, albeit on the losing side, of the American Revolution.

Grace, whose diaries and poetry are preserved in the Library of Congress, has become a major figure both in American Colonial history and Women's history. Deserted by her husband, a prominent Loyalist and British Civil Commissioner in Philadelphia, she was left to the mercy of the advancing Rebel forces under George Washington after the British fled from Philadelphia in June 1778.

Although initially under the protection of Major General Benedict Arnold, now an American byword for treachery but then a Rebel commander, she was driven from her house and estate and made virtually destitute. Legend has it that she assisted Arnold in his abrupt defection to the British cause by smuggling letters hidden in a hollow quill pen. She died in 1782, as the locket is inscribed.

That she was unimpressed by her husband's behaviour is suggested by one of her surviving poems: "Never get tyed to a man, for once when you are yoked, tis all a mere joke, of seeing your freedom again."

Charterhouse valuer Chris Copson said: "We are delighted to have these two pieces which really are quite extraordinary links with this fascinating period. They were brought in by a well-known Dorset family and may well have come to the county via the Nickelson family who had connections with the Growdens. She was also romantically involved with a Mr Milner, who was an Excise officer in Poole."

These two pieces of Georgian jewellery, estimated at £600-1000, are being sold as part of the Charterhouse two-day sale on November 10-11. Contact 01935 812277 for further information.