The head of this pin hold an ultra fine painting called 'grisaille'. It measures only approx. 15mm. The little painting represents a cupid feeding a dove on a cloud. It is set in a 18k gold, decorated frame and bears a French essay mark. It dates back to around 1860-1880, when the grisaille painting was a most popular form of art. The painting technique, by then by the people and for the people, dates back to another era and purpose.
Grisaille  simply means 'grey-ed' or 'greyed' and stands for exactly that: a painting in tones of grey. The first examples known of grisailles appear in frescoes in Padua, Italy, at the beginning of the 14th century by painters like Giotto. Since then in remained a staple in the painting world, travelling from century to century. By the time art became province not only of the church, but also of the people,  we are in the early nineteenth century. The grisaille became a much loved technique for painting portraits or, such as in this case, tiny romantic scenes.  This little pin dates back to that period, somewhere between 1820 and 1880.
On this pin, the little angel, or putto extends his arm to feed a small dove, landing on his hand. You can see his little wing, fluttering in the wind behind his back.