This is a Bohemian Czech art glass vase, circa 1900.
The vase is in a rose bowl shape, and it is 4 ¼” high and 5 ¼” wide at the belly.
The interior glass is black. The outer glass is an oil spot, with different colors in different lights and an applied iridescence. I can see blue, purple, green and sometimes yellow or gold.
The edge of the mouth is polished flat with some nibbling (fleabites) around the interior edge.
The bottom is slightly concave and smooth.
There are no nicks, chips or cracks, other than the nibbling around the interior edge of the rim.