These are from a set of twenty illustrations to a 1948 edition of La Duchesse ou la Femme Sylphide by Rétif de la Bretonne, which was published in a very limited edition of about two hundred copies.
Nicolas-Edme Rétif (or Restif) was born in the Burgundy region of France in 1734. As a young man, after a religious eductaion by the controversial Jansenist sect, he was apprenticed to a printer in Auxerre.
He married in 1760 and about six years after this had his first writings published, having moved to Paris.
Over the course of his life Rétif wrote over 200 hundred books covering many subjects, although many of them he self-published and printed himself.
He wrote many novels and short stories, a book attacking the Marquis de Sade's book Justine (the two men disliked each other intensely), a book calling for the regulation of prostitution and a sixteen volume autobiography, Monsieur Nicolas.
Having lost a lot of money during the turmoil of the French Revolution he was later favoured by the Thermidor movement, who had ousted the original revolutionaries, but his aristocratic friends and his reputation counted against him. Napoleon came to his rescue and offered him a position in the police ministry but he died, in 1806, before he could start the job.
We have been unable to find out anything about the book, other than the fact that it was written in 1783. Perhaps someone knows more about it.
The sexual acts depicted in the illustrations are varied. The final two, here, show female to female and female to male postillionage, which are rather more unusual in erotic illustrations such as this.