The AUR overprint, pictured here on SG 172 and SG 219, was used by the Welsbach Incandescent Gas Light Co. Ltd. Mantles and gas burners made by the company bore the AUR trademark.
In 1886 an Austrian scientist called Carl Auer von Welsbach discovered that a bright light could be generated by heating a knitted cotton fabric soaked in thorium using coal gas flame. This light was brighter than the light generated by any other known source of light at the time and the Incandescent Mantle was born.
Welsbach patented his invention and in 1887 the Welsbach Incandescent Gas Light Co. was set up to manufacture incandescent mantles around Europe. In 1890 Welsbach was able to improve upon his invention after discovering that a new mixture containing thorium and cerium gave off a much whiter light and produced a stronger mantle.
The Welsbach mantle revolutionised gas lighting and the coal gas industry. Initially incandescent mantles were used only for street lighting. However, they soon made the first big contribution to industrialisation towards the end of the 19th century by providing daylight like illumination in factories and work shops. Incandescent mantles soon found a wider application in domestic lighting, camping lighting, railway signal lighting and navigation signal lighting for ships.
Even with the great improvements provided by the Welsbach mantle, by 1910 gas lighting could no longer compete with electric lighting for economy, convenience and safety. The Welsbach Incandescent Gas light Co. Ltd. shortened its name to the Welsbach Light Co. in 1900 and over the following years diversified into the production of stoves, cookers and electric lamps.