FRANCE (1955) Sainte-Claire Deville*. Trial color proof strip of 5. Invention of improved method of aluminum production. Scott No 760, Yvert No 1015. Hard to find!
AVAILABLE AT $80
SENEGAL (1964) Titanium extraction*. Trial color proofs in strip of 5. Scott No 231, Yvert No 236.
AVAILABLE AT $75
SENEGAL (1964) Cement factory*. Trial color proofs in strip of 5. Scott No 232, Yvert No 237.
AVAILABLE AT $75
SENEGAL (1964) Phosphate quarry at Pallo*. Trial color proofs in strip of 5. Scott No 233, Yvert No 238. Crease in selvage.
AVAILABLE AT $75
SENEGAL (1964) Phosphate quarry at Taiba*. Trial color proofs in strip of 5. Scott No 234, Yvert No 239.
AVAILABLE AT $75