Mr Dinsdale, who is described as one of the most dedicated Nessie hunters, shot the film on 21 April 1960.
Since then, it has mainly been tourists who have sighted the Loch Ness Monster – and recorded their findings on film.
There were a spate of sightings on video in the mid-90’s, which tailed off towards the millenium.
It was only in late 2014 that the next video evidence of the Loch Ness Monster emerged.
Yet perhaps the most infamous video of them all was shot by Glasgow postman Bobbie Pollock in 2002.
The video, which is said to be three minutes long, is alleged to offer near-conclusive proof of Nessie’s existence.
However, much like the elusive Loch Ness Monster, his film remains inaccessible to the public.