I believe it's tbe bottom of a hanging oil lamp... They have like a Tiffany lamp look... And many were converted to electric, because tbe glass was beautiful.
Edit... Sorry I didn't read down n see it was ID'ed. I got excited cause I knew what something was.. Lol
Although I don't know the dimensions, it looks like a planter that would have been on a trellis. Looking at the last photo, it appears if you turned the handle, it would open the slots at the bottom, thus releasing water to allow the plant to drain. Of course, my speculation may be in vain since I don't know what size it is.