It appears to be a fairly typical screw barrel 'pocket' or 'coach' pistol that was pretty common in the mid to late 1700s and into the early 1800s.
I've heard of Dawes, and there's some indication that this may have been brothers Samuel and William Dawes, actually of Birmingham. The appear to have been active in the 1790s through about 1820.
There are any number of guns apparently made by them shown on the net.
"The gift which I am sending you is called a dog, and is in fact the most precious and valuable possession of mankind" -Theodorus Gaza
Baby Jesus cries when the fat redneck doesn't have military-grade firepower.