There are some resources that can help you a fair bit. I am one of the lesser ones.
1. If you remove the barrels, and photograph the flats, someone with an offhand knowledge to proof marks can tell you where they were made a Crown over a V means the London proof house.
2. On
doublegunshop.com there are folks with reference books for London gun makers. You can find out when and where Perkins operated from them.
3. Parts are pretty hit or miss, mostly the latter. For starters pull the nipples, go to a hardware store and find out what sized nuts they mate with--figure Whitworth, cause it doesn't get worse than that.
4. If it's a London percussion double, it's Damascus, so you would like to know the barrel thickness all the way down, the condition of the bores, and a way to proof it before using it. Damascus is much maligned, but it's all old, probably over 150 years in the case of your gun. If it's safe, figure light loads and F or FF black powder.
