unused Block Larger Than four 1a. black on blue, an unused upper left corner block of ten (3x3+1); light crease partially crosses upper row. A scarce multiple. S.G. 3, £420

Details
unused Block Larger Than four 1a. black on blue, an unused upper left corner block of ten (3x3+1); light crease partially crosses upper row. A scarce multiple. S.G. 3, £420