Hi Iain, that information was very useful. I've got an earlier version of John Walter's book, and the cylinder design/overall length quoted for the LG24 correspond to my rifle's details. The stock has two reinforcing dowels close to the rear of the cylinder for extra strength. The very basic sights look to be integral with the rest of the gun, not added later. The gun still shoots very nicely, even though it has obviously had a lot of use. Many thanks for your help in solving my mystery.