It was also functional to the plot of the movie Thunderbolt and Lightfoot (1974): https://en.wikipedia.org/wiki/Thunderbolt_and_Lightfoot https://en.wikipedia.

It was also functional to the plot of the movie Thunderbolt and Lightfoot (1974): https://en.wikipedia.org/wiki/Thunderbolt_and_Lightfoot https://en.wikipedia.org/wiki/Thunderbolt_and_Lightfoot very likely the 1965 Brinks vault robbery inspired the screenplay, but in the movie it was an anti-aircraft 20 mm: https://en.wikipedia.org/wiki/Oerlikon_20_mm_cannon https://en.wikipedia.org/wiki/Oerlikon_20_mm_cannon