Which famous military product design was originally created in 1942 to help identify friendly vehicles during WWII and later became a highly successful commercial brand?

Military insignia and logos have long served as powerful symbols of identity, unit cohesion, and national pride. Many have become iconic product designs recognized worldwide, transcending their military origins to become cultural landmarks. This trivia tests your knowledge of one of the most famous military product designs that has evolved from battlefield identification to commercial success and global brand recognition.

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WD-40 lubricant (originally Water Displacement, 40th formula)
Jeep (from the military designation 'GP' for General Purpose vehicle)
Ray-Ban Aviators (designed for US Army Air Corps pilots)
The Swiss Army Knife (standard issue for Swiss military personnel)