Believe it or not, small ceramic devices known as "pie birds" were popular circa 1930's-1940s, in home baking. Pie birds, were literally made to look like small birds with their beaks open, pointing up. These novel inventions allowed steam to vent, from top crusts.
Currently, if they can be found, original "pie birds" are quite collectable.
brtedi
PS--Sorry, Jerseygal, I didn't see your post before I wrote this...My appologies.