The Talisman Ring by Georgette Heyer (William Heinemann, 1949)

I found this one in an op shop on the outskirts of Melbourne.

"Miss Georgette Heyer's "The Talisman Ring' has the authentic 18th-century atmosphere; with its embroidered waistcoats, jewelled snuff-boxes, lace handkerchiefs, quizzing glasses and what-nots.  But inside her brocade coats and silken breeches she never fails to provide real flesh and blood animated by the ardours and foibles common nature in each and every period . . .  It is indeed compounded of all the time-honoured ingredients--love, adventure, murder, robbery, a missing jewel, and a woman's wit.  Could anyone ask more?"

--John O'London's Weekly.

It's the second printing of the first Australian edition of The Talisman Ring.

—And this book is still in print throughout the English speaking world today.  Unlike most of Georgette Heyer's romance-writing contemporaries, her books continue to sell well.  I suspect her sense of humour is to blame, because underneath the romantic trappings and historical trappings of her plots she never takes her characters too seriously!