Steve;
I have a gun which falls within your preferred time frame, W & C Scott & Son 12 gauge Bar in Wood Pinfire. It carries no serial number but has the customer's name engraved into the top rib, William D Kennedy of Louisville KY. I contacted a Mr Crawford with info on it & he suspects it was made between 1863 & 1865. It carries a Matthews Patent bolting system which consists of a center pivoting top lever, but not the Scott Spindle, with a single underbolt. The locks are the smoothest working locks I have ever had the privilege of handling, though I have not handled many truly high-grade hammer guns. I purchased it from a Louisville collector & he had tried to get info on Mr Kennedy but could find neither a birth nor death certificate for him in Louisville. All he could find was he was issued a business license to operate a Jewelry Store which included the time frame this gun is estimated to have been built.
Thanks, 2-piper. The sound and feel of cocking a well-made hammer gun lock is special, which is why I much prefer hammer guns.