Two Nazis for the Price of One - S3-E17
Visible crew/equipment: A string is seen attached to Colonel Klink's cap that is used to yank off the cap after Colonel Mannheim fires his pistol at Klink.
Some of Their Planes Are Missing - S3-E2
Visible crew/equipment: When LeBeau, Carter and Schultz enter the visiting Germans' quarters, when the door is open you can see the sound stage floorboards are uneven in front of the door to the neighbouring barracks.
Visible crew/equipment: After Hogan goes down into the tunnel in Klink's quarters, the stove moves back in place. As it does, the wire on the floor pulling the stove back in place is visible.
How to Win Friends and Influence Nazis - S3-E7
Visible crew/equipment: When Hogan gets up in the hotel room they're all in, the shadow of the boom mic plays on the wall he heads toward.
Visible crew/equipment: As Klink's car pulls up, and Klink comes around the front of it, the shadow of the camera is visible.
Answer: It's a comedy, not a documentary.
stiiggy
Perhaps it was counterfeit. There are numerous episodes where they deal in counterfeit monies.