Help with ammo box

Hello everyone I was wondering if anyone could help me with this old heavy wooden ammo box my parents moved into a home in the early 80’s the house was built in the early 1900’s and it had a very elaborate bomb shelter and this was in there I am guessing it’s Japanese writing but the box has american stamps on the inside it measures 33”x8”… thanks for any info.

 

Google thinks it's Chinese (Taiwan):
Car-loaded artillery shells for box ammunition

Maybe someone will chime in that can tell the language and read what it actually says. Makes more sense for it to be Japanese...

 

Maybe that the stamp indicates that the box was examined and had been determined to have no importance to them as far as intelligence was concerned?

 

it's so nice.... I don't see handles..... so I'm guessing not your average ammo crate.

the slots inside suggest something is being held in place..... but what ?

 

Thank you everyone for the feedback always good to hear input just one of the items that I always remember growing up and thought was so very cool Unfortunately both parents had passed away early in life so now it’s something that I enjoy and just wanted a little more info on it. Thanks again everyone.

 

@the blacksmith