First the mandatory admonishment
Now that THAT is out of the way- have you looked at the water table for markings? Open the shotgun, removing barrels from the action, turn over, and look at the flat part under the breech. You may need oblique lighting, and a magnifier.
Genuine Armory Steel was a mark used by Crescent Firearms, 1893-1930, and also by Meriden Fire Arms, 1905-1915. The phrase doesn't really mean anything except that the barrels are not laminated steel.