Looks authentic with the exception of the grip plates that have been replaced. Have a look here for maker info. Yours is listed and it's a good reference for others who may have similar inquiries.
Nambu World: Type 30 Bayonet Manufacturers’ Marks
As to value ... if you can find a buyer wishing to collect what I feel is possibly a GI modified item then it will have value but otherwise I'm afraid it will be limited. In original configuration it would retail for 80-120 USD depending on condition. Perhaps others will see it differently.
i agree with stu with original wood grips removed that takes away a lot of value i could see 40-60 tops no more !!