This replica of a Coolus ´D´ Haltern helmet is based on a find at Haltern in Germany. 
Includes a padded cotton cap for wear underneath the helmet

Details: 

Material: brass (approx. 1 mm thick - 18 gauge)
Suitable for head circumference up to 60 cm
Long distance (back to front): approx. 21 cm
Short distance (ear to ear): approx. 18 cm
Weight: approx. 1.6 kg