Continuity mistake: After the prisoners have loaded the truck, they stand around and the tailgate of the truck is down. Major Hochstetter arrives and we see the tailgate is raised. Next scene it is again in the lowered position. (00:17:40)
Other mistake: In the tunnel where the prisoners are storing ammunition. Col Hogan tells his men the next one that lights a cigarette gets a court martial. The tunnel is lit by open flames. (00:06:00)
Continuity mistake: Carter and Hogan are in Klink's outer office when Hogan takes a piece of paper off Carter and folds it into a square. Klink arrives and grabs the paper which has now unfolded to a rectangle. (00:09:10)
Answer: It's a comedy, not a documentary.
stiiggy
Perhaps it was counterfeit. There are numerous episodes where they deal in counterfeit monies.