On a slightly related note, Nikk also suggests another appearance of these helmets in an episode of Sea Hunt, a TV show from 1961 for which I also remain equally ignorant. It either didn't make it across the pond or else we hadn't invented television in England back then. Not being even a twinkle in me pater's optics at the time I shall rely on others to confirm any details relating to this. And if you can point me towards a good image from said episode. (Astronetts / Aquanetts ?) I'll post it up for all to see.