The
J-C 28 is a manufacturer's mark. It indicates the machine was made by Toyota. It's not a model number.
When you find the model number you might try Relics {
http://www.tias.com/stores/relics/ }
or SEW USA {
http://www.sewusa.com/index.htm }.
Some good photos would help us get you closer to identifying the machine. There were literally hundreds of brands made in Japan during the post WW II era.
Joe