My guess is that it's a one-piece fairy lamp.
Fairy lamps are small candle lamps or night lights.The small tea-light or votive type candle sits on the dish, & radiates its soft glow through the shade or dome that rests on the dish/base.
They have been made from the 1880s to the present day,in all different types of glass, & many shape & design variants.
Usually they are in 2 or even 3 parts, but Fenton made some 1-piece ones.
Yours is pressed glass, but I'm not certain of age or maker.
Maybe it is Fenton.....or probably of American origin at least.
Try putting a small candle (eg. a tea-light) in it. It will look very pretty!
Hope this helps!