help identifying punch bowl silver base - unmarked

[meredith72]

I bought this punch bowl from the estate of a 95 year old woman. She had a lot of German, French, and American pieces in her home. The base of this bowl is detachable, and it was heavily tarnished. It cleaned up beautifully and doesn't have any rubbing through black (that I think would suggest silver plate) The base alone is also a surprisingly heavy piece, but I couldn't find a mark nor a mark on the glass... Does anyone know anything about this piece?