The Antique - S5-E12
Character mistake: Schultz states "In Hammelburg, they call me die Glitterzehe", which is a literal (but wrong) translation of the term "twinkle toes." That term does not exist in German, and even if it did, it would have to be GlitZerzehe, because the German word for twinkling is 'glitzern', the word 'glittern' does not exist.
Crittendon's Commandos - S5-E25
Character mistake: To have an excuse not to start up the truck motor, Schultz claims his driver's license has expired. German driver's licenses don't expire.
Six Lessons from Madame LaGrange - S5-E22
Character mistake: The SS guard salutes Major Hochstetter with his palm out, in the British fashion. Firstly, German soldiers salute palm-down, secondly, by the Wehrmacht (and SS) military protocol, he should just click his heels and not salute at all when receiving an order.
Answer: It's a comedy, not a documentary.
stiiggy
Perhaps it was counterfeit. There are numerous episodes where they deal in counterfeit monies.