Experimental lamp with filament of compressed plumbago (19th century term for graphite). Filament is die-cut with dies originally used for bristol board filaments from late 1879/early 1880. Filament attached via copper plating method as became standard on Edison lamps by 1881. Filament failure likely cased by resistance built up at one attachment "clamp" point having poor conductivity causing the copper to melt as well as vaporize.
