CZECHOSLOVAKIA (1970) Town Hall Tower*. Cornerstone*. Series of 4 die proofs showing colors added, final one with all colors. Bratislava. Scott No 1700, Yvert No 1798. Czech proofs are very rare - only 2-5 were ever made!
AVAILABLE AT $250
FRANCE (1973) Tower - Toulouse*. Die proof in black signed by the engraver DURRENS. Scott No 1378, Yvert No 1763. Philatelic Congress.
AVAILABLE AT $140
FRANCE (1982) Montlhery Tower*. Die proof in black signed by the engraver DURRENS. Scott No 1816, Yvert No PRE176. Only 23 exist. Rare!
AVAILABLE AT $80
MOROCCO (1933) Tower of Hassan in Rabat*. Die proof in brown with value tablet empty. Scott type AP2.
AVAILABLE AT $120