This looks like a nice example of a late period swivel.
From what I've read, Charles Roth either knew, or worked for Nicolas Hawk as a young man, and after Hawks passing took up making swivels using more or less Hawks design and his patchboxes.
A couple others I've seen have used a trigger guard release to allow turning of the barrels, but this one looks like it uses a side plate release instead. On this one, Roth has used a regular back action lock, and also deleted the use of brass down the sides of the barrels, so would guess it is a late one even for him.
All in all a nice honest looking rifle that shows the progression from Hawks earlier swivels to a more modern (for the time) example.
John