I was told by a friend of mine that the JF in JF1 stands for Joyful Fashion. I guess it is a Japanese expression. Steve, the seller has had one of these before. He puts out some really nice tractors and equipment. I bought my dozer from him.
I don't know what the body is made of but it is a factory Hinomoto body. I believe they had 2 different models. If I remember correctly they were built around an E1804 chassis/engine.