These beautiful crystal cups and saucers were made in the 1840s by Baccarat.  They are most unusual as they were made in rainbow hues of lavender, purple, blue , pink and green.  
They were made to mix with each cup and saucer being a different color. It is unlikely for them to survive over 150 years but these remain a complete set.
As you examine this glass you can see and feel the ripples as it was blown and formed by a talented and inspired glass artist nearly 2 centuries ago. One of the reasons such glass is universally appealing is that we share a collective memory of color with an iconic rainbow.
The cups are club shaped and the saucers slightly cupped with a center well. It was customary in early times to pour one’s drink into the saucer to cool before returning it to the cup or to drink from the saucer.  Remember, hot liquids were usually coming straight off a fire and were much too hot to drink without cooling. Liquids meant to be served hot were often kept in kettles resting in fireplaces or on cook stoves.
Tea was likely served in these cups as they are smaller, more like a demitasse cup. 
With tea costly, it was often served in small quantities.  Having tea placed you in high stranding in your community.
High tea costs are hard to imagine as we can get tea just about anywhere today.  What is easy for us to buy was once reserved for royalty and those with access to the finer things in life.
I love the idea of adaptive re-use.  I have easily used these and other cups, plates and bowls for many things with beautiful results. The small handle on the side makes it easy to hold and eat. 
I have used them for chocolate mousse with candied orange peel, spiced whipped cream over mandarin sections, crab salad in antique plates with garnishes and chicken salad with homemade dill crackers.
Also lemon curd over Benne Seed Cookies from Ole Colony Bakery in Mt. Pleasant dotted with whipped cream and she-crab soup with a firm endive leaf as the spoon.
These are just a few ways you can adapt your antique or inherited pieces to make a memory with a table of distinction. Using them as they were originally intended is ideal. Things made by artists are superior to things made en masse today.  It will be a pleasure for you and your guests to use these lovely relics of the past.
SPICED WHIPPED CREAM
Using a small carton of whipping cream, beat until soft peaks form.  Add two tsp of fresh squeezed Meyer lemon juice or 2 tsp pomegranate juice. Beat a little longer adding 1/2 cup of sugar. 
Ladle over cookies, fruit or cake. 
Refrigerate any left overs.
SAVORY
Using a small carton of whipping cream, beat until soft peaks form.  Add two tsp of chopped, fresh basil, 1/2 tsp salt, dash of pepper and 1/2 tsp of the juice from a jar of capers.  Whip again until stiff peaks form.  
This is fantastic over baked chicken breasts or as a sauce for raw or poached oysters or fish. Refrigerate left overs.