Many signboards in the film are written in a sans-serif typeface, which was highly uncommon in the 1940s. The business sign of the photographer who takes the pictures of Glavonja and Kalauz is written in either Arial or Helvetica font, both of which were devised decades after the WWII.
The star on a Yugoslavian flag on the wall of the partisan interrogation room has a golden border. The golden border wasn't present on the flag until 1947, so during the WWII, it should have been just a plain red star.
Throughout the movie, there are various modern day buildings and/or air condition device visible in the background.
Some of the children playing football in front of Glavonja's house wear modern day sneakers.
When the receptionist speaks about Glavonja and Kalauz to Beme, he switches their fake names.