In the later Middle Ages, the crown came to be seen as a heritage from the Kingdom of the Lombards and was used as regalia for the coronation of some Holy Roman Emperors as kings of Italy.

According to early modern scholars such as Bartolomeo Zucchi and Ludovico Antonio Muratori, the small size is due to a readjustment after the loss of two segments.

According to tradition, St. Helena, mother of Constantine the Great, had the crown forged for her son around a beaten nail from the True Cross, which she had discovered.

Pope Gregory the Great passed this crown to Theodelinda, princess of the Lombards, as a diplomatic gift, although he made no mention of it among his recorded donations.

The Byzantines then sent him the diadem, holding the helmet (which was exposed in the cathedral of Hagia Sophia) until it was looted and lost following the sack of Constantinople in the Fourth Crusade in 1204.

[citation needed] King Theoderic then adopted the diadem gemmis insignitum, quas pretiosior ferro innexa(s)crucis redemptoris divinae gemma connecteretas (Ambrose, De obitu Theodosii) as his crown.

As for other Germanic populations, the ritual of accession was an acclamation by the armed people in the royal palace of Pavia, during which the sovereign received a lance as symbol of his power.

[4] Lord Twining cites a hypothesis by Reinhold N. Elze that Gisela, the daughter of the Emperor Louis the Pious who married Duke Eberhard of Friuli, may have originally possessed the crown and left it to her son Berengar I of Italy on her death in 874.

[5]: 424 Finally, Twining cites a study by Ludovico Antonio Muratori which documents the various degrees of the ecclesiastical authorities alternately authorizing and suppressing the veneration of the Iron Crown until, in 1688, the matter was subjected to be studied by the Congregation of Rites in Rome, which in 1715 diplomatically concluded its official examination by permitting the Iron Crown to be exposed for public veneration and carried in processions, but leaving the essential point of whether the iron ring came from one of the nails of Christ's crucifixion undecided.

However, subsequently Archbishop Visconti of Milan gave his own decision that "the iron ring in the Monza crown should be considered as one of the Nails of the Holy Cross and as an original relic.

[7] Thirty-four supposed coronations with the Iron Crown were counted by the historian Bartolomeo Zucchi from the 9th to the 17th century (beginning with Charlemagne).

Seated upon a throne, he was invested with the usual insignia of royalty by the Cardinal-Archbishop of Milan and, ascending the altar, he took the iron crown, placed it on his head, and exclaimed, being part of the ceremony used at the enthronement of the Lombard kings, "Dio me l'ha data, guai a chi la tocca."

Speculations have been made that the silver circle was added by the goldsmith Antellotto Bracciforte, who restored the crown in 1345 to reinforce it given that the (presumed) theft of two plates had weakened the hinges.

The Italian film La corona di ferro (1941), directed by Alessandro Blasetti, tells a story about the arrival of the crown in Italy.