Mike,
Here are my observations:
The rib matting is not a pattern used by H&A, their predecessor F&W.
The rib pattern is similar to Colton and Union F.A. Co barrels but the lug and cocking hook is not.
The barrel hanger is a Deeley type? Any patent dates?
The other maker that used a similar rib pattern was Torkelson. The early Torkelson models had dolls head extensions and a different lug design, but the last model has an extension and top bolting that matches your barrels. I believe Daryl Hallquist might be able to provide an answer.
https://www.doublegunshop.com/forums/ubbthreads.php?ubb=showflat&Number=75887&page=allJohn
