As a matter of course I check all my stamps under both long wave and short wave lamps as well as natural light.

I have a number of the above stamps all identical ( more or less ) in both natural and under long wave light.

However under short wave light while most react with varying intensity of white, one produces a bright yellow reaction. Also on this stamp ( and a couple of others ) the engraving reacts with a strong purple hue, and appears much sharper than normal.

Are these recognised variations to the normal, and has anyone any bright ( groan -pun warning) ideas as to the reasons. I thought the yellow might be some sort of contamination from the soaking process- I only collect used stamps, but I am at a loss about the other phenomenon.

I guess being a low-value "make-up value" stamp it was probably in circulation for a long time with multiple reprints. These are not often thoroughly studied as being too "modern" to be philatelically interesting.

Thanks in advance for your thoughts !

 
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tomiseksj

23 Aug 2018
05:13:48pm

re: 5c 1990 Luiz Munoz Marin

The Marin stamp issued February 18, 1990 (Scott 2173) had overall tagging and is the one that lights up under shortwave UV.

An untagged variant was released in 1991 (Scott 2173a).

A stamp with tagging omitted (Scott 2173b) appeared before the untagged variant was issued.

I have 10 copies of the Marin stamp in my duplicates -- only 1 is tagged.

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