The Counterfeit Countess was published in December 1983 by Signet for author Diana Campbell. This is the second book of hers illustrated by Allan Kass and it is the story of Selina, who poses as the wife of Lord Worsham in order to gain access to high society while he is trying to gain a fortune from his very strict grandmother.
Allan Kass creates an elegant cover of our couple at a ball. They stand outside and our heroine is dressed in a teal gown with gold accents. I like her matching jewelry and tiara. Note that our hero wears a velvet jacket and lace cravat! Allan initials this book in the lower right corner.
While this plot makes for fun reading, it's assumed that it wouldn't have happened in regency days. Any female spending the night with an unmarried man would have been ruined and have needed to marry immediately.