The attached picture was sent to me by someone Out There. It was bought off eBay and seems to have been tagged as a 'practice helmet', which makes little sense.
Described as being made of 'fibre plastic', whatever that means (maybe even bakelite, but it doesn't resemble any of the usual British WW2 commercial products) it apparently has the legend GOEDGOKI ARB P.U.4 either printed or impressed into the leather sweatband (the owner is unclear about which). The 'GOEDGOKI' bit sounds strangely familiar but I am presently unable to put 1+1 together successfully.
Any ideas? Not obviously a British commercial product, maybe a Third World clone? I dunno.