The first of the greeting cards features artwork by Mike Edwards of the biblical figure Adam in the buff leaning on a tree in the Garden of Eden. The text on the card reads, "Adam came first. Men always do!"
"What's the definition of the Perfect Man? A midget with a 10-inch togue who can breathe through his ears!" the second card reads.
That card featured the back of a man's head kneeling before a woman wearing just her underwear.
Both cards were from the GirlsTalk series of greeting cards that were published by Emotional Rescue around 1987. It was not immediately clear when they were given to King Constantine, known as Tino.
"I couldn't decide which card to send & then thought you'd enjoy both!" Diana had scrawled in one of the cards.
Diana died in a car accident in 1997 when she was trailed by aggressive paparazzi while in Paris with her boyfriend, Dodi Fayed. Tino, who reigned from March 1964 until the monarchy was abolished in Greece in 1973, died in January.