Ken, I was following the auction on Gun Broker. It is unusual to see a Quality 4 with stepped lock plates. The barrels were cut but only 1/2" so there is still choke. It looked to have a sloppy fit on the recoil pad and someone got carried away with the polyurethane.
As you stated, has features found on early Fulton guns, narrow convex ribs on receiver, looks to have the slanted breech balls.

I do have pictures of 19182 a Qlty 4, completely different, large convex ribs, rounded breech balls that almost touch the locks.

There are mysteries that we will probably never figure out.

One of our members has a Gr. 5 2207x, top of barrel Hunter Arms Makers, Fulton, N.Y. has the rounded receiver lug, typical Fulton engraving for a Grade 5. Did the early Fulton guns of 1889 start their serial numbers after the last Syracuse serial numbers in the 22,000's? But, I also have serial number in that 23000 range that do have the squared lug, but no maker's name on barrel, also I have one that goes as high as 36992 a Qlty 3/Gr.3 10 gauge that has a squared lug, convex ribs, large breech balls that does have Hunter Arms on the top rib.

The hammer guns aren't as confusing to figure out age.

Unless the records from Syracuse surface, we might never know.