The Hanging Key

The Hanging Key is a symbol denoting a contact point for members of the Whisper, the secretive agents of House Nechtan that watch over Travelling Ensembles. The key used is of a very old style, and is hung up somewhere in the display of a shop, inn, or other place of business. The proprietors of these establishments act as coordinators for the organization, and keep track of agents in their area of influence.
These places are safehouses and communication centres for Whisper agents. Spies can relate word to assassins of any targets and pass on information about useful recruits or noteworthy events to interested parties, as well as turning over the fees paid by ensembles under their protection. The person running the business, called a host even within the organization to avoid suspicion, is expected to provide a number of services, including a safe place to stay, a secret way out in case of emergencies, and sufficient medical care to treat an agents wounds, if necessary.
The key used is made from a single rod of bent iron, with the ends forming the teeth of the key, and hangs from the tip of the key that would normally be inserted into a lock rather than the loop that would normally be used. It is often well hidden in the display - tucked behind wine glasses at an inn, for example - and if someone asks about the key, the proprietor will deflect, saying it's an heirloom or a curiosity that some traveller left as collateral and never returned, for example.
An agent of the Whisper hoping to make contact follows a specific exchange. First they ask after the key. After the proprietor deflects, they offer to purchase it for 6 copper pieces. The proprietor will ask if they know of a place that can use such a key, and the agent claims they have a chest back home that they've never managed to open. The exchange concludes with the proprietor offering to discuss the matter further in private.