Funny Thing Happened on the Way to London - S3-E5
Other mistake: When Lieutenant Bauman starts speaking German, his last two words "especial mission" is said in a decidedly French accent. The correct German phrase would be "Sonderauftrag." Non-German terms like "Mission" were generally avoided in the Wehrmacht for ideological reasons.
Answer: It's a comedy, not a documentary.
stiiggy
Perhaps it was counterfeit. There are numerous episodes where they deal in counterfeit monies.