The osmium filament lamp is one that wasn't utilized to any extent in the United States, in part, because of the advent of the tungsten filament lamp. It was manufactured in Austria and Germany and was marketed in Germany and Great Britian. By 1905 the Vienna firm stopped producing the lamp. The trade name under which the lamp was sold in England was "Osmi", in Germany the name was "Auer-Os" and in Austria it was called "Osmin". It was the invention of Carl Ritter Auer von Welsbach.
The English 50-volt 25-cp lamp, marketed by the General Electric Company, Limited, of London, had a filament length of approximately 15 inches and consisted of three separate hairpin shape filaments connected in series. Lamps were also available at 2.5 cp and 4 volts, 5.5 cp at 8 volts, 10 cp at 25 and 33 volts, 25 cp at 45 to 60 volts and 32 cp at 70 to 75 volts.
Because osmium was a rare and expensive metal the lamps in 1902 were rented and not sold, so that the user would eventually return the lamps to the manufacturer. In 1903, when a lamp cost $1.25, the user could recoup $0.19 if the burned out, but unopened, lamp was returned within 18 months. In that case the filament could be treated and reused.
Of especial interest are the support wires that retained the filament loops. In general the lamps could be burned only in the vertical position with the bend down. This was necessary because the filaments would sag otherwise and possibly touch the bulb wall or each other. The supports
