This is a two-way mirror. I've got the other one of the pair.
http://jp.y42.briefcase.yahoo.co.jp/bc/just1bit_me/lst?.dir=/TwoWayMirror
http://www.helloproject.com/news/messe_0524.html
http://www.sanspo.com/geino/top/gt200405/gt2004051804.html