To find these types of weapons is not surprising, since it's easy to conceal a knife in a product, and it's very likely somebody will buy it. But are these types of deceptive objects actually used for violence and are they effective as weapons, or are they merely novelties?
Here's a quiz: which one of these items does not conceal a knife?
- Belt buckle
- Key ring
- Walking cane
- Tool card
- Money clip
- Playing card
- Credit card
See discussion at Schneier on Security>>
(Which item does not contain a knife? None. They all do.)