When Hogan pours out the contents of the briefcase, all the bits of paper are square. When the gang is putting them together, they are all curvy and misshapen.
When Sergeant Schultz enters Klink's office while Klink is painting, the Luftwaffe eagle and swastika are positioned backwards on Schultz's jacket. The eagle on Schultz's chest should be facing left towards his heart, but is facing away to the right. His backwards swastika is not properly displaying its vertical lines on the upper left and lower right sides, but has them backwards on the upper right and lower left sides. This is another of many appearances throughout this season that the costume department issued Schultz's factually wrong uniform jacket.
When Klink enters the barracks while the gang is working on putting the map back together, the map pieces blow from the table toward Baker, implying that the wind from the door came in and circled around and back to Baker (showing that the fan - or whatever was used to blow the paper - was off-camera to the left). The pieces should have blown toward the camera.
There are overhead electric wires seen in the background of some of the outside shots.
When Klink enters the barracks while the gang is working on putting the maps together, the door is open for a second before the pieces of the maps blow off the table. The pieces should have blown off immediately when the door was opened.
When Klink stops outside the art gallery he parks beside two 1960s-era VW "bugs". The wartime Bugs looked slightly different.
Production lights are reflecting off of Klink's monocle in some scenes. Update: One good one occurs when Klink, Schultz and Hogan are at the gallery. After Rhona leaves to get the three 'collectors', Hogan walks over to Klink and says, "Well, that's it, sir.". Then Klink turns his face away from Hogan and gets a full reflection of a stage light in his monocle.