This piece was recently "picked" in Pennsylvania and purchased at the Show of Shows by me in Louisville.  I have not taken the cover off the helmet, as it looks like it was "grown in place" - I am afraid to move it for fear of disturbing decades of settlement.  Pictures will provide a better description than I could.  This really is a spectacular specimen.  Showed it to several WWI helmet experts, none of whom could fault it.  Age and wear is consistent throughout the piece.