Cachet depicts a light beam passing through a prism to create a spectrum. Stamp depicts colors of the spectrum. The 15th Colloquium Spectroscopicum Internationale was held May 26-30, 1969 in Madrid, Spain.
First Day Cover commemorating United Nations efforts for the cessation of nuclear testing and preservation of humanity
Cachet and stamp depict a mushroom cloud from a nuclear weapons test. Cachet was created by Fleetwood and the stamp was commissioned by the United Nations Postal Administration. Postmark depicts the United Nations…