This unusual piece is an Imhof model 75/845 8 day night clock modelled on earlier Victorian candle lit types of similar shape.
The movement is horizontally housed in the split glass sphere, the hour wheel rotating the lower hour hemisphere and the minute wheel driving the upper minute hemisphere. I am unsure of the calibre of the movement, which is wound from the cylinder under the sphere. The time is set by rotating the hemispheres and is indicated by alignment of the hours and the minutes with a vertical indicator.
This particular model differs from others I have seen in having a raised, as opposed to a flat, light button at the top. A small battery is fitted under the button and illuminates the white sphere when pressed