what the heck is a Namiki DF-100 Direction Finder

I was at salvation army (which is a sometime bountiful hunting ground for ancient audio) and I found a Namiki DF-100 Direction Finder. It's a small, blue metal box about 5 x 2 inches. On the back is Japanese writing and an a diagram of an amp and cord. There are two buttons on the front and 4 indicator lights. Anyone have any idea what this thing is? How to work it? Thanks tons
I believe it's a device that will tell you if your component is in correct polarity when you plug it in, or if you need to reverse the plug. It actually makes a difference for at least some European items (i.e., both my Jadis JA80 amps were inverted polarity, I had to reverse the plugs on them). I have no idea how to work it.
I actually have one of these devices that I bought new in the mid-eighties from The Tweak Shop. I keep it in its original box with instructions. If you require instructions, I can fax them to you if you provide me your fax number. It is used to correctly plug in a component's AC power cord in its correct orientation with respect to absolute polarity. Basically, you first disconnect all interconnects from the component. Then, plug in the supplied mini-connector into the unit and attach the other end to the component's chassis via an alligator clip. Next, you power up the component and push the appropriate button on the Namiki to power it and take a chassis voltage reading. Then, the AC plug is reversed and a second button is pushed and...Presto! The Namiki tells you which connection orientation is correct. Although the device works very well, I have never noticed any sonic differences in either orientation. Also, one spade of a component's AC plug is larger and the plug usually has a 3rd safety prong, so a cheater plug is necessary to do the test. Finally, if the Namiki shows that the AC plug must be oriented backwards, than the cheater plug must be left in place - ugh! It kind of makes me sick to think that I would need to put a cheap cheater plug on my very expensive exotic AC cord - that may degrade the sound more than having the thing plugged in the wrong orientation in the first place - how appalling! Hope this helps.
Seasoned has it largely correct. The device senses dc leakage voltage and goes with the orientation of the plug that has the lowest voltage. I would disagree, however, on how frequently you hear a benefit. You can accomplish the same using a volt meter and a contact to ground. You touch the chassis or a grounded part and go with the lowest reading.

If you hear a difference and are a purist, you can reverse the connections to the ac plug within the unit and get the results you want without using a cheater plug.

I bought a Namiki long ago and probably have not used it in 15 years. Since most of my equipment is by small manufacturers, I find that they consider this.
As I recall, there were reliability issues with this thing, so if it doesn't work for you, don't blame yourself. Good luck, Dave
Tbg writes:
"You can accomplish the same using a volt meter and a contact to ground. You touch the chassis or a grounded part and go with the lowest reading."

I beg to differ. When you check leakage against ground, as you suggest, you're measuring "leakage against ground", which is helpful, but this is NOT what the DF-100 does.

It does not measure "against" anything. It is a single lead sampling device that detects an electrostatic field. Since these fields can have the equivalent "zap" power of several kV, it is helpful to minimize these, especially to protect solid-state electronics.

But truthfully, I don't quite understand how it works.

I've discussed my theories in my current EBay listing (I'm selling mine), but I must admit that I'm perplexed how it detects "proper polarity", with no ground connection.

Could this be a really advanced gadget that is not recognized because of lousy instructions? Or quackery?
radioman, I always wondered how the Namiki worked without a ground, but in probably 20 instances where I tried the volt meter versus the Namiki, they gave the same results. I also like to know the voltages both ways. Sometimes I am shocked by the high values.
Seasoned- Would you still have a copy of the Namiki instructions that you could share with me?  I recently purchased one but the previous owner did not have the instruction sheet.
You will need to open the unit and make sure a 9 volt battery is connected. First thing you do is to connect the alligator clip to some part of exposed chassis, or a ground connection if available. I usually loosen a screw attached to the chassis if its available and clip it to that exposed head.   Sometimes I take the cover off and attach to the metal chassis.  With the clip secured you need to turn on the unit (top button) ... then while it stays on for a few seconds, push the memory button below. Then, you will need to quickly reverse the power cord going into the socket. Within three seconds push the memory button again. A light will indicate which position was the correct in the socket. If you have a three prong IEC cord?  You will need to get a cheap one and cut off the ground plug so you can flip the cord. If you find the polarity is reversed, it will require someone who knows how, to reconnect the power wires inside the unit. Warning: Its not safe to use an IEC plug minus the ground plug, so don’t just flip it and leave it that way. If your system is high end what you hear will make a difference. I have one component that came with a wall wart and found it needed to be placed upside down (tail side up) to be correct. It sounds better with the the correct orientation. I found only one piece of equipment that was wired IEC to be reversed. The other manufacturers were diligent to get it right.