Can anyone help with identifying this mystery unmarked "Brodie" style helmet ?

[Jc9765]

I bought this helmet a while ago, but I was never able to figure out exactly what it is.
I know it's not a British MkI or MkII, nor is it a Canadian MkI.
It's completely unmarked with a WWI style liner and a canvas chinstrap.
The only thing I was able to find was a helmet that IMA sold that is exactly identical to my helmet.
They described it as a WWI MkI Type A Brodie helmet, but I believe their description is not correct.

Original Canadian WWII 1940 MkI Brodie Helmet by General Steel Wares of Toronto with Net – International Military Antiques

I think it could be a commercially produced US Civil defense helmet.
Any help would be greatly appreciated.