When did Japan make a 7mm mauser to chamber in a type 30 carbine?

I have a wwii type 30 carbine that is 7mm mauser with a hook style saftey.Gunsmith said Italy made some for Japan but why 7mm Mauser? Or was it made in North China during Occupation?Trying to find answers and value.Has very low serial numbers in 7000 s. It was brought back as a souvaner intact and not demilled.And before you ask It is confirmed type 30 in 7mm by 57mm.