Mike,
The tubes are everything on a gun this old.You need to find out the condition of the barrels. Are they pitted and by how much? What is the wall thickness? Any thing less than .022 is too thin. Since this gun shot black powder early on, look for signs of corrosion around the firing pins.
I own a Grant and a H. Holland, both made in 1874, both with damascus barrels but with no pitting and bright bores, although the H. Holland had to be polished to clean up some minor rust, inside and out. Damascus barrels made in the 1870's for London firms are surprisingly robust. They were exceptionally well made. I shoot low pressure ammo through mine and I have had no problems at all.
Personally, I would not buy a Purdey hammer gun if it need liners.
