In the first world war they apparently shielded the wearer effectively from debris caused by artillery shells that would have otherwise killed them. Here's an i

In the first world war they apparently shielded the wearer effectively from debris caused by artillery shells that would have otherwise killed them. Here's an interesting video about the statistics behind it (and how they were misinterpreted at first): https://www.youtube.com/watch?v=1IQE0uZUMys https://www.youtube.com/watch?v=1IQE0uZUMys