Dr. Ralph Brooke (N.Y.?) imported them, interesting thing about these kits was that most were cut/kitted in the homes of Japanese families after the war.
Polk's hobbies and America's Hobby Center both stocked them, and in 1969, I had the good fortune to fine a whole stock in Oakland, (Hobby Hut, Telegraph Ave.?)
I have an F8F Bearcat, in the familiar heavy brown cardboard carton: It is labeled with 'U-CONTROL', .29-.35; there were others with the same label, 'U-CONTROL'
Skyraider, P51 Mustang, Corsair, and the multis: B36, Connie, B24, B25, Bamboo bomber. (wish I'd grabbed that one!)
These would build heavy, (I had a Zero, it weighed almost 5 lbs.! But it flew...) the wood is like a 'gummy' basswood, but easy to copy in balsa. It is like buying a kit with patterns for everything.
If it weren't for Keith Trostle's help and Al Rabe's Bearcats, I would have built mine from balsa, and been happy...but thanks to these fine gentlemen, I am now spoiled and know too much! (grin)
But when I find a chance to buy these Japanese kits, I jump at it. They are magnificent in my memory of what truly 'deluxe' kits were.