2011 Federal duck stamp mini-sheet of one, picturing white-fronted geese by Jim Hautman (his fourth federal stamp). The mini-sheet, issued in a quantity of 10,000 is missing the artist's signature. The reason this is considered an error is because the signature was the "value added" that allowed the Duck Stamp Office to sell the sheetlet for a premium over the cost of the stamp.  Scott Catalogue value is $175.