I have Sc J12 and & J14 that show either shading of the entire design or double impression. The 10c J12 shows a light red shading (double impression???) that matches the entire design. The 50c J14 shows a green shading or double impression that also matches the entire design but not as neatly as the 10c. Scott also calls out the J14 as greenish blue. Mine is black with the greenish color underneath. Can anyone shed some light on this?
https://www.wikitimbres.fr/co/timbr...le-francaise A microscope cannot distinguish the light emission from the pigment. Your digital camera can;but you have to look for it. Another reason that in the catalogs this stamp is indicated as black is that from the day the stamp was released ; the official records listed it as black.That does not mean that during the actual printing the real black ink used ;but a very dark blue green (almost black).