At a glance this item seems to be perfectly typical, but it conceals a spring-loaded blade deployed by pressing a switch when it is used to make an attack. A creature observing it only realizes that the item is a weapon with a DC 15 Investigation check (made with disadvantage if the weapon is being worn at the time and not deployed). Once deployed, a bonus action is required to resheathe the blade. You gain an expertise die on your attack roll when you deploy this weapon as part of an attack against a target that is unaware you have it.