The First World War.
Produced “in association with Imperial War Museums,” this is a mini-encyclopedia of Great War tanks, planes and ships, presented in the form of flash cards.
The set features British (20 cards), German (15 cards), French (9 cards), Italian (2 cards), Austrian (1 card) and Russian (1 card) fighting machines. Two of the cards display a very brief timeline of the war.
The cards are printed in color, but they’re not color-coded, and although military armament is usually painted in drab colors (except for aircraft), there’s not much detail to the illustrations, but for that, a novelist or other adult researcher would probably consult other sources, anyway. Even most injection-molded plastic model-building sets come with more information than the cards supply about authentic appearance, so they would be of limited utility even to hobbyists (of any age).
The cards constitute only a quick reference guide; that said, they may have some value for a homeschool history assignment.
Not worth their list price, but if you can get them at a deep discount, they may make an interesting gift for a child whom you’d like to encourage to study military history.