... just read in the Georgano encyclopaedia that Ohta started serial-production of small cars and trucks in 1922, and that their business was bought out by Kurogane, another Tokyo car'n'trucks building company, in 1957.
It seems the PH-1 didn't lasted long, and used the same type of side-valved 4-cylinder as many Ohta cars, a 903 cc producing a meagre 23/24 bhp...