The international spy museum is no more than 10 kilometers from where 3 of the Russian agents lived just outside Washington. And near the entrance to the exhibit are photos of uncovered Soviet spies. In a separate room is _________________________________. 

This is a car from a James Bond movie. On a normal day, this would be a hit of the exhibit, as would the pistol made to look like a lipstick and a lethal umbrella. But on this day, in light of the spy scandal, perhaps the most popular display is_________________________________. It contains a hidden message. Historian Mark Stawt says this method of passing on data was used by the recently deported Russian agents. 

"In this particular case, we have a purchase order. And then, underneath it, we have a secret message hidden, which comes out under ultraviolet light. _________________________________. It's been around for centuries and the Russians used it in this recent case."
 

(1)what is called the Spy School
(2)this unremarkable piece of paper
(3)There are many different ways of doing this, but this is a very traditional technique