An AH Fox SP (or SPE if it has ejectors) Grade.
Quite a rare shotgun, especially in 20ga.
Made in the early 30's to the mid 30's+.
The 'Skeet' and the 'Upland-Skeet' SP's were appointed with a small amt of engraving. The plain SP/SPE grade was void of any scroll but sometimes has simple border work on the metal.
Factory options included a single selective trigger (Fox/Kautzky system same as used on the other high grade AHF shotguns.) Straight grip or pistol grip, choice of butt plate or pad, bbl length and chokes, ivory bead sights ect.
The finish was a change from the original Fox post WW1 Cyanide case color hardening. These got a Blued finish often descibed as a black oxide coating finish. Something like the Baker finish used on their Black Beauty perhaps.
I fitted a forend to a customers SPE/16 a couple years ago that had a Factory set of extra bbl's.
The ejector forend metal parts were all 'in the raw' ,,orig Fox parts from a Gunsmithing/Parts outfit in the Adirondacks. Included a hunk of wood that kind of looked like a BT forend with a rough out cut inletting.
Got it all together and functioning.
Fitted to the extra set of bbls and also made both forends ( the other was a splinter) fit either bbl set. Checkered the wood on the BT to match orig Fox pattern. MAtched the wood finish and color. & on & on.
Very happy customer,,
then he told me he sold it.....
I suspect the OP's gun has been restocked.
The lack of checkering is the biggest thing.
The would quality is outstanding!,,The American Walnut blanks used to do the job must have been pricey indeed. Looks like something I normally see on a Grade 5 Model 21.
Congrats on a beautiful classic American SxS.
It'll handle just about anything in the field or target coarse you want it to do.