How is the appearance datatype used in BLE adverts?

The GAP service supports an appearance characteristic which is a 16 bit value used to associate the device with a generic category. For example the appearance characteristic could be set as generic phone, thermometer or bar code scanner. A complete list of possible GAP appearance values can be found on the  Bluetooth.org  website under assigned numbers https://www.bluetooth.org/en-us/specification/assigned-numbers This appearance information can also be made available in an advert using the appearance data type (0x19) so that a central device can display an icon representing the the generic device type of the peripheral device.