10/18/21 - This is a 1950s experimental X-51 helmet. This helmet was intended to replace the M1 US helmet and had several benefits including a lighter weight and having better shrapnel protection when tested. However there were more downside qualities to this helmet and it was never adopted after field tests. This helmet comes with an original liner, as shown in excellent condition. Original chin strap also in tact. Some mild exterior shell wear but no major damage.