BELGIUM (1968) Windmill in Bokrijk. Ministerial proof. Scott No 653, Yvert No 1461.
AVAILABLE AT $50
AUSTRIA (1976) Windmill, Retz*. Black proof. Scott No 965, Yvert No 1348.
AVAILABLE AT $20
TONGA (1990) Windmills*. Chromalin proof in full color from printer's archive. Scott No 743, Yvert No 775. Only 2-3 exist. Rare!
AVAILABLE AT $100