That's No Lady, That's My Spy - S6-E17
Factual error: Hogan tells Carter that the bush he's camouflaging himself with is poison ivy. Poison ivy is not native to Germany, the very few wild plants that exist today descend from those introduced to botanical parks after 1942.
Answer: It's a comedy, not a documentary.
stiiggy
Perhaps it was counterfeit. There are numerous episodes where they deal in counterfeit monies.