This works and I doubt if this F. Williams was the maker
https://www.doublegunshop.com/forums/ubbthreads.php?ubb=showflat&Number=174888

Looks to be 1868-1875

[Linked Image from photos.smugmug.com]

"Laminated Steel" on lower quality guns usually means Twist
I agree the barrels were almost surely cut.
If the chamber was bored out to 10g and barrels honed, careful measurement of the wall thickness from breech to muzzle, by an expert, is required. Please let us know the chamber and bore dimensions.