Short answers, pulled from the story.
The Gjermundbu helmet is a Viking Age helmet restored from nine excavated fragments and now on display at the Museum of Cultural History at the University of Oslo. It has a round shape, is made of iron, and is built from four plates.
The Gjermundbu helmet was discovered during field clearing in 1943, with the initial find made on the 29th of March that year at the Gjermundbu farm near Haugsbygd in Ringerike, Buskerud, Norway.
Farmer Gunnar Gjermundbo found the burial while leveling ground to build a house for his parents. Archaeologist Sverre Marstrander and museum assistant Charlotte Blindheim were then sent by the University of Oslo to investigate and confirmed it was a rich Viking Age man's grave.
The Gjermundbu helmet is on display at the Museum of Cultural History at the University of Oslo. The Gjermundbu farm where it was originally found sits near Haugsbygd in the municipality of Ringerike in Buskerud, Norway.
The Gjermundbu helmet is one of only five known Viking Age helmets and one of only two complete enough to have been reconstructed. The grave it came from, Gjermundbu I, is probably the richest Viking Age man's grave in Norway apart from the Gokstad and Haugen farm graves, and it is the only known Viking Age grave find in Scandinavia or Western Europe to contain both a helmet and chain mail.
Alongside the helmet fragments, the Gjermundbu I grave contained fragments of chain mail, a ceremonial sword of Jan Petersen's type S, two spears, two axes, four shield bosses, two spurs, and five or six bits. A second, less wealthy grave in the same mound, Gjermundbu II, held a double-edged sword of type M, a battle axe, and a spear head.