Extremely dark ambers are often refered to as Black Glass since where the glass is thickest light has dificulty passing through. The true Black Glass still isn't really black but a dark olive that is completely opaque even in the thin sides of Mason jars. Direct sunlight will not pass through. Only a paper thin flake will pass light and show as olive. Along with the Royal jar bottom are shards of a wax sealer, Mason's Patent 1858 threads, a rim area of a Royal and a substantial chunk of Black Glass. More extreme Hemingray Go-Withs!