The Top Secret Top Coat - S2-E29
Continuity mistake: When Hogan and company are getting ready to listen to the sock from "Aunt Alice" they plug the coffee pot up to their recorder. As they do so, the light that indicates power is lit up, but then Lebeau plugs in the power cord.
The Top Secret Top Coat - S2-E29
Factual error: In Klink's quarters, there's an (obviously fake) banana in the fruit bowl. Bananas were luxury items in Europe in the 1940s, and certainly so in war-torn Germany. The majority of Germans didn't have access to exotic fruit until the 1960s, and fake fruit of this type wasn't available then either.
Answer: It's a comedy, not a documentary.
stiiggy
Perhaps it was counterfeit. There are numerous episodes where they deal in counterfeit monies.