Pistols with turn-off barrels were made well before the reign of Queen Anne (1702-1714). My father had several that dated from the late 17th century. A style of turn-off barrel pistol became popular during Queen Anne's reign. These usually had a barrel that resembled a cannon, locks incorporated into the breach with side cocks, silver decorations, walnut stocks and silver butt-caps that featured a grotesque mask. Pistols of this style became known as "Queen Anne" pistols.
The pistols shown below are of the box-lock style. English boxlock pistols began to appear around 1730 and lasted well into the percussion era of the next century. With a boxlock the cock (hammer) is located in the center of the lock on top of the action. The flashpan and frizzen are located just in front of the cock on the center of the breach. The frizzen spring is fitted into a recess on top of the breech. Most boxlock pistols have a trigger guard safety. Sliding the trigger guard forward with the pistol half-cocked, locks the trigger and the cock. The box-lock in the first post has a type of safety common on smaller pistols. It is located on top of the action behind the cock.