A friend sent me this today, so I thought I would pass it on How can you tell when you are in a room, restroom, motel etc. with a mirror or a2-way glass? Here's how: I thought it was quite interesting! And I know in about 30 secondsyou're going do what I did and find the nearest mirror.... Do you know how to determine if a mirror is 2-way or not? This is not to scare you, but to make you aware. A policewoman who travels allover the U.S. and gives seminars and techniques forbusinesswomen passed this on. When we visit toilets, bathrooms, hotel rooms, changing rooms, etc., how many of you know for sure that the seemingly ordinary mirror hanging on the wall is areal mirror, or actually a 2-way mirror (i.e.,they can see you, but you can'tsee them)? There have been many cases of people installing 2-way mirrors in female changingrooms. It is very difficult to positively identify the surface by just lookingat it. So, how do we determine with any amount of certainty what type of mirror we arelooking at? Just conduct this simple test: Place the tip of your fingernail against the reflective surface and if there isa GAP between your fingernail and the image of the nail,then it is a GENUINE mirror. However, if your fingernail DIRECTLY TOUCHES the image of your nail, thenBEWARE, FOR IT IS a 2-WAY MIRROR! "No Space, Leave the Place" So remember, every time you see a Mirror, do the "fingernail test." It doesn'tcost you anything. Remember: "No Space, Leave the Place" Ladies: Share this with your girlfriends, sisters, daughters, etc. Men: Share this with your wives, daughters, daughters-in-law,mothers,girlfriends and/or friends.

Wow I had this one years ago, amazing how they keep going. I did lots of reading when I first got it and from what I can gather if its 'two way' its a window with a special one way type coating but as my memory is eluding me on it this link might explain it better!

http://urbanlegends.about.com./library/blmirror2.htm

I did check mirrors for a while, and never found one to be two way glass thank Heavens!