The Black Windmill is a 1974 British thriller directed by Don Siegel, based on the novel Seven Days to a Killing by Clive Egleton and starring Michael Caine as MI-6 agent John Tarrant whoes son is kidnapped. The ransom is half a million pound sterlings in uncut diamonds which is the exact amount that MI-6 prepared for funding some operation. Only special service personnel is aware of the diamonds, and Tarrant's boss Cedric Harper (Donald Pleasence) suspects that Tarrant himself staged the kidnapping.
In the opening scene a fake Royal Military Policeman (John Rhys-Davies) carries a revolver in holster. The holster appears to be a Pattern 1937 which was issued for Webley .38 revolvers so Webley .38 Mk IV would be a best guess.
M1911A1
In the scene in Paris, Drabble (John Vernon) is seen with an M1911A1-style pistol. Later he gives it to Ceil Burrows (Delphine Seyrig).
Walther P38
In the same scene Drabble's henchman carries a Walther P38.
During the hunt for Tarrant in Paris a fake policeman fires an unidentified pistol.
Submachine Guns
MAC-10
In the final scene Drabble (John Vernon) and Pinkus (George Lane Cooper), one of his henchmen, are armed with MAC-10 SMGs, most likely in 9x19mm version. John Tarrant (Michael Caine) manages to disarm Pinkus and uses his MAC-10 in the final shootout.
Other Weapons
Firearms in MI-6 Shooting Range
Numerous handguns and long guns are briefly seen in the scene in MI-6 underground shooting range.