With so many sportsmen switching to the new-fangled pinfire breech-loader, there must have been a certain amount of peer pressure. What to do if you couldn't afford the 10-25 guineas to buy a decent pinfire from one of the popular makers? Well, you could take your trusty muzzle-loader to Thomas George Sylven of London, and have him convert it to a pinfire, one of his specialties. A much cheaper option until a showy new gun could be had, and that old muzzle-loader wasn't going to get much use anymore!
This gun is a 16-bore converted around 1865 with a muzzle-loader barrel by Richard Seffens, who was in business in London in the 1820s (the original Seffens gun might have been a flintlock). What is interesting is that Sylven uses what we now know as the skeleton butt plate, with iron top and bottom and wood visible in the centre. This is the only pinfire I have ever seen with a skeleton plate.