CAMEROUN (1972) Chemical apparatus*. Die proof in green signed by the engraver COMBET. President Adhijo prize. Scott No 545, Yvert No 525.
AVAILABLE AT $140
FRANCE (1956) Paul Sabatier*. Catalytic chemistry*. Scott No 793. Yvert No 1058. Die Proof in black.
AVAILABLE AT $140
MONACO (1971) Alchemist*. Radar*. Rocket*. Die proof in black signed by the engraver JUMELET. UNESCO 25th anniversary. Scott No 807, Yvert No 856.
AVAILABLE AT $160