Source of archive footage?

Does anyone know the source of the archive clips that are incorporated into the concert footage? It looks like it's from an old classroom film on energy sources, or even an energy firm's publicity/propaganda. I'm sure it's in the public domain now.

I thought the use of it was fascinating, how specific portions were colorized, certain images were frozen or slowed down, and phrases like "big generator" were emphasized.

The film credits Charlex for creating the special effects, and this site lists three uncredited actors as appearing in the archive footage.

Does anyone have any more details? Just curious.