This is an antique, late 19th century, Victorian era, plant stand from about 1890 that is constructed of cast brass metal, onyx stone and marble. These were quite popular in homes during that era and were often adorned with ferns in Asian jardinieres. The most prolific manufacturer of this type of stand was Bradley and Hubbard. If you look around the metal areas there may possibly be a "B&H" stamped or cast into the surface. The open bottom register indicates there was at one time either a matching marble inset shelf piece or one that was either inset or had a round/oval hole cut into it for another plant pot. The estimate is based on actual recent past recorded auction sales.