UNITED NATIONS (1970) Power lines*. Mekong river*. Map of delta*. Set of 10 imperforate progressive proof pairs. Scott No 205, Yvert No 199. Lower Mekong River Development. From the UN printer archives. Rare!
AVAILABLE AT $100
AFARS & ISSAS (1975) Ampere*. Electric apparatus*. Trial color proof. Ampere is considered the father of electro-magnetism and was also a noted mathematician. Scott No C92, Yvert No PA107. Not easy to find!
AVAILABLE AT $15