Which packaging innovation revolutionized the distribution of slide rules in the 1950s-60s, contributing to their peak popularity before electronic calculators?

The packaging of mathematical tools and instruments has evolved significantly over the centuries, reflecting both technological advancements and changing educational approaches. From ancient calculation devices to modern graphing calculators, how these tools reach consumers has shaped their adoption and use in mathematics education and professional practice. Test your knowledge about how mathematical instruments have been packaged and marketed throughout history!

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Plastic protective cases with belt clips, making them portable for engineers and students
Cardboard tubes with humidity control, similar to blueprint storage
Metal tins with foam inserts, primarily used for high-end models
Leather folding wallets with multiple compartments for different slide rule components