When the three goons roll their ammunition down a table to decide who will execute De Fenouillet, the rounds roll in a straight line. Since the three of them use 357 magnum revolvers, the rounds have a rim which would make them roll in an arc of a circle.
When Bazil picks up the brass to determine who manufactured the ammunition which struck him in the head, the name of the manufacturer is stamped on the back of the brass, as is the norm, but there is no primer. Instead, the stamp occupies the entire surface.
Marconi's son responds to the cue "Nagasaki" with "17 kilotons". The atomic bomb that was dropped over Nagasaki in 1945 had a blast yield of 22 kilotons.