I got this helmet at a yard sale. I am wondering what year it is from, possibly WW2 era? I see it is Swedish by the decals. It looks like an M37 but it only has the two bolts (don't know what they are called) viewable on the outside of the helmet, one on each side holding the leather chin straps on. The M37s I have seen online look like they have many more bolts on the outside of the helmet. Are there different versions of the M37? I don't know much other then what I read so any information would be a big help. Any value to this helmet?