MONACO (1967) Marie Sklodowska-Curie*. Chemical apparatus* and atom symbol*. Full sheet of 30 trial color proofs. Scott No 673. Yvert No 732.
AVAILABLE AT $475
MONACO (1979) Albert Einstein*. Relativity equation*. Trial color proofs in full sheet of 30. Scott No 1194. Yvert No 1203.
AVAILABLE AT $475
PANAMA (1965) Nuclear powered space vehicle*. Imperforate essay in unissued colors. Scott No 460e, Yvert No PA353.
AVAILABLE AT $50
GABON (1967) Atomic symbol*. Trial color proofs in strip of 5. IAEA. Scott No 216, Yvert No 215.
AVAILABLE AT $80