This is an example of many different kinds of cast iron gem pans; Basically small muffin pans, in different shapes.
These pans became popular in the 1800's, when they were given away free with the purchase of a new cast iron stove.
At first, large pans with a dozen or more molds were in demand, due to the large farm families. By the 1950's, families became smaller, so consumers wanted smaller pans with fewer molds.
These pans were originally used for making "gems", a variety of simple breads made from whole wheat or graham flour. Then it evolved into other types of bite sized treats and small desserts.
There are thousands of gem recipes found in old cookbooks. You can browse some old cookbooks on this site.
Or you can make this sample recipe, which I have not tried, but to me looks appetizing:
1 cup self rising flour
1/2 tsp salt
1/4 tsp celery salt
4 tbsp butter
1/2 cup finely chopped celery
2 tbsp grated cheese
1/4 cup milk
Mix flour, salt, and celery salt. Cut in butter with pastry mixer. Add celery and cheese. Add egg and milk. Mix into a soft dough. Bake at 350.