Cachet depicts the wavelength of krypton-86, which was formerly used to define the meter from 1960 until 1983. A meter was defined during this time as the wavelength of the 605 nm (orange) spectral line of a krypton-86 atom. The stamp depicts the international treaty signed by France and 16 other countries in 1875, to coordinate use of the metric system, and krypton-86 is depicted in the postmarks.
|Place of publication|
Mendoza, J. “First Day Cover Commemorating the Centenary of the Convention Du Mètre (Treaty of the Meter).” France, 1975. Witco Stamp Collection, Box 1. Science History Institute. Philadelphia. https://digital.sciencehistory.org/works/qz20ss53m.
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