On the British Film Institute (BFI) web site there is a page called "Britain on film map":

https://player.bfi.org.uk/britain-on...147472039/6///


Which has two film clips with footage from Caithness:


Claude Friese-Greene on his trip around 1920s Britain:

https://player.bfi.org.uk/free/film/...ad-2006-online

This has some footage of John O'Groats from 47:26 minutes until 49:18 minutes of this film clip from 1926 (no sound).


Engines at Dounreay:

https://player.bfi.org.uk/free/film/...ow-1957-online

This has some footage of Dounreay from 3:04 minutes until 11:25 minutes of this film clip from 1957.