Galaxy Police File 21 Jan 99 
 David is reported to have said... 

Given what the plaque says, it should be obvious why it has a 
Japanese translation.

Just a thought here. 
Let's assume, for the sake of argument that the Jurai 
colonized Earth (which in the OAVs they did, by the way). We 
can assume that the Jurai colony on Earth is located in Japan. 
(we know from TMiL that Jurai energy can be harnessed at the 
Five Fudo). Wouldn't the Juraian writing be recognized as being 
the same as that found on old Japanese wall hangings displayed 
in museums?