The Flame Grows Higher - S1-E31
Revealing mistake: As Hogan, Le Beau, and Newkirk help Schultz up the slope to the "forest fire", there is lumber stacked across a low spot in the top of the bank and covered with "snow" and grass. Probably meant as a path.
Answer: It's a comedy, not a documentary.
stiiggy
Perhaps it was counterfeit. There are numerous episodes where they deal in counterfeit monies.