peter:
The Kerr's Pattern revolver is often listed in texts on British revolvers, and is regarded as something of a milestone in the development of the percussion handgun. The best source would be here:

BTW, I took a couple of hurried photos of the Webley Bulldog in my collection. It will get a tidy-up one day to clean up the stains, but is near perfect internally so a good shooter in the meantime.