Maybe a simple way to think about it is this: Curie was a Polish-French physicist, and so a collector would more expect her to be honored by a postage stamp iss

Maybe a simple way to think about it is this: Curie was a Polish-French physicist, and so a collector would more expect her to be honored by a postage stamp issued by Poland or France... and indeed she has, more than once. I also see some Marie Curie stamps issued by French colonies, which was probably thought to contribute to the unity of the empire.