https://www.medievalists.net/2025/03/medieval-great-helm-leads-highlights-at-apollo-auctions-this-weekend/
Bit of a polish and it'll look as good as new
Always sceptical when a new helmet apparently without provenance before the 1980s turns up. However, they have an expert report and a scientific analysis, so who knows?
Whatever its age, someone seems to have used it for target practice.
Add : A bit of googling shows this particular helmet has failed to sell on two previous occassions, so others may have similar reservations.
And that's the danger....provenance not the target practice
It's a popular style for forging. Some are old Victorian forgeries, which have an interest of their own, but quite a lot of modern stuff intended to look "as found".