A sign

The "A Sign" was a business license issued to restaurants and adult entertainment establishments in Okinawa that were officially approved by the U.S. military. Starting in 1953 and continuing until its abolition in 1972, it was awarded to businesses that met the hygiene standards set by the U.S. Military Discipline Enforcement Committee. The "A" stood for "Approved," and approved establishments displayed an "A" mark in front of their stores. The purpose was to protect the health and welfare of U.S. military personnel and their families by complying with hygiene and building standards.

Also, the color of the letter "A" varies depending on the industry.redis a restaurant,blueCabaret, etc.blackwere color-coded according to food processing.