It is not an original by any means, though it is reasonably faithful to many New England style underhammers such as the Ruggles in outside appearance. If you look at the inside the workings are completely different. I am not sure who makes the action, but I have one that I think was built by the same person that I purchased on Ebay some time ago. I was intrigued by the way they operated which though not original, is quite clever.
One problem with mine, and yours is that it only has a full cock notch, not safety. This is faithful to this style of pistol, but has always made me a bit nervous. I have also found that the sear engagement on mine is not safe due to the angles used, it is possible for the hammer to slip. This may not be an issue with yours, but it is something to watch out for.