Did the book cassette away at Christmas the same 2x and the enthusiasm was great. I have chosen this copy of the book vault, because the sites are "real" and really you can not tell from the outside that it is a cash box. When you open the book cover or the key resides in the empty cartridge you can of course guess that something is wrong here. When traveling, one could therefore recommend easy to fasten a rubber household to books, so it does not accidentally pops up. Or placing it under another, "real" book ... recommended otherwise unrestricted. Looks very high, really and truly does not fall as a "safe" on!
No guarantee for theft (finally you can book easily in your pocket), but perhaps safer in some places as the hotel safe, which is everybody knows, like open from hotel staff!