With one-piece almond shaped skull with characteristic stalk, the base retaining a few original rivets, downturned brim with guttered and rolled rim. Stamped with the arsenal mark for the Barberini family. 

Notes:

This helmet is from a group which appeared on the market in 1978. Originally sold at auction house Wallis & Wallis. 

The Barberinis supplied armour for the Papal Army in the late 16th Century. Maffeo Barberini became Pope Urban VIII, 1623-1644. His brother, Taddeo, was made Supreme Commander of the Papal Army.