Was it used in the Spanish Civil War? by either the Nationalists or the Republican armies? I know the one with the lug nuts on the side were.

404 Not Found -"French Style"

Czech M30 -"German Style"

Czech Model 1930 Civil Defense Helmet w Liner Original Scarce | eBay -M30 Civil defense.

Are these all the same type of helmets aside from mild variations? Please forgive my ignorance.