The flintlock ignition system developed around the year 1550 in the Low Countries of Europe. The lock action was simple: a pivoted cock held a piece of flint between two jows; when the trigger was pulled, this cock snapped forward to hit a steel face and shower sparks down into an open pan filled with priming powder. This new weapon was the basic weapon of the American Revolution and to remain the principle military arm in North America and Europe until the 1840s. It did however, appear in four variations during its three hundred years of service.
The fundamental difference was that the steel batter which the flint struck was separate from the pan cover. The flat cover was slid clear of the pan at the time of frining - initially by hand, and later by mechanical means. Its advantages included less cost to produce and maintain, and greater reliability and faster firing. Also, it could be carried while loaded and primed.
The prevalance of the Snaphaunce in America seems to be very little. Few specimen and fragments have been found. The assumption is that the ascendance of the English Lock technology quickly superceded its innovation and usefulness.
2) English/Dog Lock
Refinements in the flint system accelerated firearm development during the early 1600s. The English Lock ushered in two major innovations. First, the separate frizzen and pan cover of the Snaphaunce were combined into one piece on a single pivot. Second, features were added to secure the cock in a locked position prior to the firing. One of these was a sear moving horizontally out through a hole in the lock plate to hold the cock back in its firing position until the trigger was pulled. The more popular method was to mount a small dog catch on the outside of the lock behind the cock. This "dog" was then hooked manually into a notch in the rear of the cock to prevent it from slipping forward for a premature discharge while loading. The sear type of arrangement lost favor about 1650, but the dog-lock feature continued in use by the British even on later styles of locks until about 1720.
The English/Dog Lock seems to be the most popular model of flintlock used in America until the early 18th century. More Dog locks and fragments have been found in private and public collections than any other previous firearm.
Coincident with the evolution of the encased lock action, another variation came into being along the shores of the Mediterranean. Like the English lock, it combined the pan cover and frizzen in one piece. The most noticeable difference, however, was the location of a mianspring on the outside of the lock plate. This meant that less wood had to be cut out of the stock for the lock's internal mechanism, and permitted a larger spring to better utilize the poorer quality of flint in those countries.
4) French or "True" Flintlock
What was to prove the ultimate flint action and reign for more than two hundred years is believed to have been perfected by the French between 1600-1610. It simplified existing actions in two principle ways: the horizontally moving safety sear of the English Lock was replaced with a new vertical sear, which operated wholly within the lock to engage notches cut into the tumbler. In addition, a second notch was provided in the tumbler to permit a safety half-cock position.