Barov Peasant Caller

The Barov Peasant Caller is an heirloom bell that belongs to the Barov family. When the bell is rung, the peasants of the Barov lands will be summoned to defend their lord and lady. It summoned three Servants of Weldon Barov for the Alliance and three Servants of Alexi Barov for the Horde.

As the trinket was made unavailable with the Cataclysm expansion, only those who already have the trinket can summon the Barov peasant servants.

Source
This item is a reward from the quest The Last Barov (quest) which starts with:
 * Weldon Barov in the Chillwind Camp in the Western Plaguelands
 * Alexi Barov at the Bulwark in the Tirisfal Glades