I might be stating the obvious but the 44-410 used 44/40 shotshells,the 44Gamegetter, or 2 inch.410.The 44 Gamegetter cartridge also was available loaded with a single ball. So a gun with "choked" barrels was marked "Not For Ball".
Very cool guns. Built to a price point on the lower end. Not readily found in the condition you describe. Sounds like a cool find.