This is a prototype example of the famous "Stopper" light bulb. This experimental light bulb was made at the Corning Glass Works. It has a beautifully crafted hand blown clear glass globe. The ground glass receptacle end of the glass globe is vacuum sealed with a solid ground glass plug called a "Stopper." This experiment was devised to determine if a Stopper light bulb design was a feasible way to seal an incandescent lamp. Westinghouse developed the Stopper light bulb design in the early 1890's as a way of circumventing Edison's remaining patents. Westinghouse was successful in commercializing his "stopper sealed" light bulb which kept his company's incandescent lamp division afloat while he waited out the remaining term of Edison's light bulb patent rights. Edison's patents only covered a light bulb which becomes a one piece glass enclosure by melting the glass in order to seal it. The Stopper was a two piece glass enclosure sealed by vacuum and glue, thus overcoming Edison's basic patent rights. This prototype Stopper light bulb, a laboratory specimen, was not intended to be electrified, however, the experiment was very thorough, electrical lead-in wires were actually embedded in this glass stopper to simulate potential leak conditions around these lead wires. The length of this prototype is 6.0 inches and it has a 3.0 inch diameter glass globe.