That is an M1 helmet, the interior looks like this (easily recognizable by the stripes)
Info:
The M1 helmet is extremely popular with militaria collectors, and helmets from the World War II period are generally more valuable than later models. Both World War II and Vietnam era helmets are becoming harder to find. Those with (original) rare or unusual markings or some kind of documented history tend to be more expensive. This is particularly true of paratroopers' helmets, which are variants known as the M1C helmet and M2 Helmets, which used special liners with multi-point retention straps to prevent undesired movement of the helmet during descent.