When I was a lieutenant stationed in Frankfurt we were issued these cards. They showed us what the license plates looked like on vehicles belonging to the Soviet Military Mission. Many of the Russians stationed with that mission were presumed to be spies, so they had us call in right away if we spotted them. That was one way they kept tabs on the bad guys. The same cards were issued to militaty personnel on Cooke Barracks asking them to keep an eye out for Russians.
I am a military brat—and I say that with great pride.