Tin with 20 sides, 1963, designed by M.C. Escher for the N.V. De Vereenigde Blikfabrieken, metal, marked with artist's monogram, with few minor scratches, soft surface dirt and few lesser defects, otherwise in good condition. 14 cm (each rib 9 cm). Issued in an unknown but very limited edition, only for employees of the factory on the occasion of their 75th anniversary in 1963. Bool/Locher, p.151.