WWII Japanese T90 Civil Defense Helmet, Exc Cond, Battle of Okinawa

Japanese  WWII Type90 Civil Defense Helmet. Purchased at garage sale circa 1965, Louisville, KY, from widow of a veteran named Krueger, whose son was a childhood friend of mine. Trophy helmet. In storage since then. Kanji on inside rim translates as "Nishihara"(Google Lens), the site of a Japanese airfield and initial U.S. amphibious assault on Okinawa (largest of Pacific theater, 180,000 soldiers, and bigger than D-Day). 425 is probably a unit designation. Nishihara can also be a surname but "Nishihara 425" was written by one hand at the same time so it was undoubtedly the town and unit. Nishihara and basically the entire island of Okinawa were totally leveled in months of fighting. Deaths were approximately 250,000 total, all sides. (Wikipedia) Much of the civilian population was conscripted by the Japanese, many starved to death, many were used as human shields, many committed suicide. 4,000 Japanese soldiers and their commanders committed mass suicide in caves towards the end of the battle. Torrential rains came and it is said the whole island was nothing but mud and maggots, as the dead were left where they fell. An absolutely horrible battle, in which even two U.S. generals were killed. Kanji on front was harder to get a translation for, tried several sources including native Japanese. Ulatus (a translation service) responded "discharge, emit, depart, set off" so I'm thinking perhaps an artillery/anti aircraft unit. The island was heavily bombarded by us before invasion by both air and sea. Helmet is in excellent condition with virtually all the clay brown paint remaining in a lustrous state. No product was added for luster and photos don't do it justice. A couple of extremely small dings to top and very minimal rust spots at very top and inside bottom. Liner attachment rings look virtually new and are free moving. I wonder if a liner was ever attached since the rivet holes appear to have paint in them and rings are lustrous. This is the fourth variation and last of the T90 line, and reportedly the rarest. They were manufactured with lighter steel because of material shortages late war and had a more flared rim, which I believe most people envision when they think of a Japanese helmet. They quit adding the four ventilation holes to the top and the rivet holes are rectangular rather than round. An exceptional piece and solid investment. I have researched it extensively and viewed past sales and this is probably the best one I've seen. Priced reasonably considering translations, condition and provenance. More photos, info on request. Secure insured shipping to US only.