The change was the liner. The early liner was replaced. Which left the distinctive slots on each side and the now unused bolt holes. Originals run in the 5 digits in value and reproductions are not easy to find. The item "WWII GERMAN M37 Paratrooper HELMET WithHand Aged Paint Work and Liner" is in sale since Wednesday, February 10, 2021.This item is in the category "Collectibles\Militaria\WW II (1939-45)\Reproductions\Germany". The seller is "gafrika42" and is located in Lakeville, Minnesota. This item can be shipped worldwide.