Here’s some more on Cinderella stamps. Youtuber and Philatelist Graham Beck. Explains everything philately in his channel. You might end up binge watching his whole channel. He presents it in a way that is fun and informative. Kids can grasp it and adults don’t find it boring.
Here’s his video on Cinderella stamp/labels.
A true postage stamp will have a denomination (either a price or rate), more modern stamps have the year they were issued, and the name of the country either in English, French, or their official language or native language.
Cinderella’s don’t.