Just got this from a family member, brought back from the Pacific by my Great Uncle, a member of the 2nd Marine Division.  My uncle kept family letters in it.  I’m told it is some sort of communication equipment box… but who knows.  Can anyone confirm or deny?  Thanks in advance.  

It is for spare parts for a 25 kilowatt DC power generator..... metal commutator brushes or something related to that. 

 

Manufactured by Shibaura Engineering Works in September 1938.

Thank you so much!!