From Paris, a carnet du bal used to hold a lady's dance cards with the most elegance and maybe also secret billets doux.
 
Dating from the 1800s it has a deep pearlescent shine and thick, high quality mother of pearl shell is beautifully carved. In the middle is a silver design with two inset semi precious stones. 
 
The back of the folder has a crack across the middle, but it is stable and still functions. The two mother of pearl covers are held together by fabric, with leather pockets inside, to make the lady's folder.
 
It measures 3.75" by 2.5"