Lincoln Jefferies started business in 1873. I think he was making shotguns up until around the Second World War but then mainly made air rifles. Technically the business still exists but now only produce air rifle pellets under the 'Marksman' brand name. I would very much doubt that the gun was made with 3 1/2" chambers as they are a fairly recent innovation. If you have an address on the top rib I may be able to narrow the date of manufacture down a bit for you. I don't think records still exist. Any pictures of the Proof Marks will also help in determining the date. A lot of the really early 10 bores had 2 5/8" chambers but also 2 7/8" and 3" also existed. Lagopus.....
