GERMANY (1982) Urea molecule model*. Specimen (overprinted MUSTER). Scott No 1379, Yvert No 981. Friedrich Wohler, discoverer of organic chemistry.
AVAILABLE AT $20
GERMANY (1975) Chemical plant*. MUSTER (specimen) overprint. Scott No 1181.
AVAILABLE AT $15
GERMANY (1983) Otto Warburg*. MUSTER (specimen) overprint. Pioneer in biochemistry. Scott No 1230, Yvert No 769
AVAILABLE AT $15