Used but still in usable shape for a reenacted or somebody looking for one to wear or display.  Look at the pictures as a reference and ask any questions Thanks

I added a picture of measurement of outside of helmet.

This is what someone told me.

Based off those the helmet looks like a size of 68-70 since they made them 60,62,64,66,68 and 70 in width I can’t remember if it’s mm or cm but I’m pretty sure it’s  cm