Space Helmets, an Evolution
1. The original 'thin chin strap' helmet from 1978
2a. A 'thick chin strap' version that was introduced because the thin version kept breaking. This one doesn't feature the side dimples.
2b. A 'thick chin strap' version, this one with side dimples.
3. The 'motorbike' version that was introduced around 1988.
4 The latest version, much more 'spacey', introduced in 2009
As always, best huge (warning - Very large image !)