Kirk here with some news for archeology fans:
"The about 55-centimeter-long iron sword was unearthed from the remains of a tomb from the Kofun period at the site of Kumamoto Castle during an excavation by the city government."
I wasn't even aware of tomb remains being located on the castle grounds.
P.S. The article shows an enhanced image in which kanji are remarkably legible.
Iron Sword Excavated in Kumamoto Inlaid with Characters Possibly Meaning Year 604
KUMAMOTO — Characters that may indicate the year 604 have been discovered on an iron sword that was excavated in April last year from a burial mound in Kumamoto City, the city government announced Friday. Previously, an iron sword inscribed with characters believed to represent the year 608 was ex...