All slaves in the Den wear collars. Each of these collars bear a tag identifying them as my property. Most simply are my house insignia. When they are initially accepted for training, they are placed in a training collar of steel chain that locks in the back with a small padlock. Fully trained slaves wear an elegant solid steel collar with a built in lock... A more permanent item, not to be wasted on those who may or may not last.
Slaves in my service often have bells or other items such as ribbons, signs, or even precious gemstones for exemplary service, on their collars, generally based on their level of training and favour. These, like anything can be revoked just as easily as they are awarded.
The coloured bells usually indicate level or type of training in my service.
A brass bell indicates that a slave has completed the first phase of training in the pens and demonstrated proficiency in very basic slave positions, serving and attitude.
A blue bell is awarded for the 2nd phase, green for the 3rd and a purple bell indicates a slave who has completed the 4th, and usually final phase of training, save for specialized training. A pink bell indicates a slave who is being trained as a tower slave or whose intimate use is restricted and red bells are for those being specifically trained as pleasure slaves.
So, for instance, the collar depicted below would tell us that the slave wearing it has completed the first two phases of training and is not available for intimate use.