2-way mirrors

Can you tell when you are in a hotel room, restroom, motel etc. with a mirror whether it is in fact a mirror or 2-way glass?
Here's how: I thought it was quite interesting! And I know in about 30 seconds you're going to 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 all over the U.S. and gives seminars and techniques for businesswomen 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 a real mirror, or actually a 2-way mirror (i..e., they can see you, but you can't see them)?
There have been many cases of people installing 2-way mirrors in female changing rooms. It is very difficult to positively identify the surface by just looking at it. So, how do we determine with any amount of certainty what type of mirror we are looking at? Just conduct this simple Test: Place the tip of your fingernail against the reflective surface and if there is a 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, then BEWARE, 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't cost you anything. Remember: 'No Space, Leave the Place'