Is the real Excalibur in a chapel in Tuscany, Italy?

At the same party, an Italian friend told me about the existence of a real-life medieval sword-in-the-stone near a small town in Tuscany.

As an Englishman, I am well familiar with the Arthurian legend of the sword Excalibur embedded in a rock, which only the young Arthur was able to extract, marking him out as the true king of all England. I am also aware that although the putative King Arthur is supposed to date from around the 5th - 6th centuries CE, the Arthurian legends only achieved popularity with Geoffrey of Monmouth's histories, written in the 12th century, possibly based on some unreliable reports from the 9th century, i.e. we are very clearly in the realm of legend here, and not history.

However, it turns out that there is a bona fide sword-in-the-stone in Montesiepi Chapel, near Chiusdino, Tuscany. The story goes that a wealthy 12th century knight called Galgano Giudotti had a vision of the Archangel Michael, who called on him to renounce all his worldly possessions. Giudotti replied that this would be about as easy as splitting a stone with his sword, but when he pretended to plunge his  sword into a nearby stone, it did indeed easily sink into the rock. Some time later, Giudotti found himself by accident at the very place he had seen in his vision, and he really did embed his sword into a rock, just as he had in his vision. For this, he was promptly made a saint, one of hundreds in Italy beatified over the centuries for totally unsubstantiated miraculous actions.

But, in a chapel built around the scene of the miracle, there is to this day a sword embedded almost to the hilt in a rock (see picture, right). No-one knows quite how this is possible or when it might have happened, but the sword design and its metal have been shown to be consistent with a 12th century weapon of the region, and ground-penetrating radar reveals a cavity below the sword that could be a burial chamber of some sort.

Some Italian academics have hypothesized that the Montesiepi sword-in-the-stone could have been the original inspiration for the English Excalibur legend. Certainly, medieval historians were not above the odd bit of colourful embroidery to make their histories a little more exciting, so who knows? As far as I know, no-one is suggesting that Arthur was in fact Italian, but this part of the story could well have been borrowed from Italy.