What is this thing thats hanging in my kitchen?

about 30 years ago i bought a round copper pan like object..it has a black handle a good two feet and the copper pan is about 20 inches across...it has 7 round indents with the reverse side dome shaped..it looks very nice in my new england kitchen but what is it?..its too big for an oven..and the quality is far to superior for a copper novelty..i bought it in a antique shop.i also bought a rolling pin i was informed over 100 years old..how would you guess a rolling pins age?