We don't know if these were intended to be used as egg coddlers.
These are barely convex ... really cylindrical with a slightly
curved in base. The lid sits on top of the body ... it's made of
aluminum with a knob handle. The backstamp says HOTOVEN,
HARKER, THE OLDEST POTTERY IN AMERICA.
These objects might have been intended as condiment jars. Some
were sold in sets of four with a wire rack.