The green one is a WW2 era British or Commonwealth Mk2 helmet. The second looks like a standard English Mk1 Brodie or possibly an American M-1917,,, I can't find that stamp on the list of known British makers, but they were made all over the British Empire from Canada to South Africa, India, Australia....And I don't have a list of American makers handy because my books are still in storage at the moment. Check the rims for any other markings if you would, and also if you could, post pics of the helmets in profile and the chinstrap bails.
In that condition which I would call just above "relic" with no liners or chinstraps, no names or unit markings, the value isn't going to be very high. You can get complete intact ones for around 100$ So... The question is, how much do sellers ask for them and what are collectors willing to pay? You may find similar condition helmet shells with asking prices from around 80$ up, but realistically if I saw them I'd offer that 80$ for both, and put them aside to possibly restore one day.
They are a neat find though, and definitely worth saving