This is a Swedish M37 Helmet

Of course. I can certainly fill you in on this helmet.

Identification

This is a Swedish M37 Helmet that has been refurbished with a later, post-war liner. These updated models are often referred to as the M37/65.

Here are the features that lead to this identification:

• The Decal: The blue shield with the "Tre Kronor" (Three Crowns) is the national emblem of Sweden and was used on their military helmets.
• The Shell: The shape is that of the standard Swedish M37 steel helmet.
• The Liner: The original M37 helmets had a three-pad leather liner. Your helmet has an updated webbed suspension system with a leather sweatband, which is very similar to the U.S. M1 helmet liner. This updated liner was added to many M37 shells during the Cold War, typically in the 1960s and 70s.
• The Size Marking: The "53-57" stamped on the liner is the head size in centimeters, not a date.

Age

The steel shell itself could have been produced anytime from the late 1930s through the post-war years. However, the liner dates the helmet's final service configuration to the Cold War era (likely the 1960s or 1970s).