This is a Cast Glass Inverted Dome with Acid Cutback etching of an
Vase with Greek Key handles and Bell Flower Draping. These details
are Classical details (1780-1840) and this fixture was probably original
equipment in an Early Twentieth Century Colonial Revival House. Perhaps
a Greek Revival. The original Period for Greek Revivals in the US was around
1840 but the form was very popular and was revived in many subsequent eras.
This is quite a unique fixture.