Anchors Aweigh, Men of Stalag 13 - S1-E16
Factual error: When Shultz is standing at the top of the ramp with a crate marked "hors d'oeuvres", talking with Carter and Lebeau, if you look to the right of Shultz's head (camera's left) you can see the Desilu Studios water tower.
Answer: It's a comedy, not a documentary.
stiiggy
Perhaps it was counterfeit. There are numerous episodes where they deal in counterfeit monies.