Willets Beleek was made by the New Jersey Pottery Co until 1914. Your piece appears by the mark to date from the latter part of production. Pieces in the 15 inch range like yours and being offered at around 175.00 - 200.00. That is an asking price, not a selling price. It is a beautiful old decorative piece for someone who is into that look. It is not that popular today as it was 30 years ago. Although that could change.
