This is probably a study for a vase decoration - the decorator's monogram is visible at the bottom left.
Pen and gouache on parchment circa 1750-80 - not framed.
At the age of 18, Heracles was invited by King Thespios, ruler of Thespiae. Anxious to have the hero as the father of his grandchildren, Thespios sends him one of his fifty daughters every evening; Heracles thus becomes the father of fifty sons. In other versions, the feat is accomplished over the course of five nights, or even a single night. The Thespiades number fifty-one, the eldest and youngest daughters of Thespios giving birth to twins. One of Thespios' daughters refuses to enter Heracles' bed; she is punished by becoming the hero's priestess and doomed to perpetual virginity.