Re: Arisaka Type 99 Rifle...
Collectors prefer and pay more for things that have not been "cleaned up" other than normal cleaning with an oily cloth, and a properly cleaned and oiled insides.
You would be well advised to have a competent gun smith familiar with Japanese WW II rifles examine it before you try to fire it. Some late war produced Japanese rifles are so poorly made that they are not safe to shoot. Also they used two different calibers in WW II.