WWII Yokogawa voltmeter

This is what I believe to be a Japanese Yokogawa voltmeter from WWII. I recently picked it up at a local flea market in a box of junk. It was made in the 19th year and 4th month of Emperor Hirohito which was verified by another site. The only markings on it in English are DP-13, No. 2429, and 1KV. All other writing is in Japanese. It has 3 ranges for voltage (30v, 150v, and 500v) with screw on-type connectors at the top. It is still in working order, I tested it and it does work. I have not been able to find much of anything on it except at one other site which had a similar meter, a DP-12, and information pertaining to the date (19.4). Any other information is more than welcome. I really don't think I have any interest in actually selling it, I'm just curious as to the history of it as I'm sure a Japanese soldier didn't just hand it over to an American soldier only to be found almost 70 years later in box of junk at a flea market in Kentucky. Finding out the actual story behind it's travels, I'm sure I'll never learn. I'm sure a U.S. soldier grabbed it as a keepsake, as it is in really good condition- and when I show it, I get to add my own of finding it. And use a now famous quote in our house made by my soon-to-be wife, Katy- "You paid $4.00- FOR THAT???.