Large Vintage Acrylic Still Life Painting in Wood Frame

You know what's great about this painting? It's lovely and very well done, but it also has a bit of a mystery. What's that large round thing? The opening to a cornucopia? A giant melon?

Measures 25-1/2" across x 19-3/4" in height x 1-1/4" in width.
Painting is 19-1/2" in length x 15-1/2" in height

Signed N. Wagner on the front.