Image is 11.6" x 13.75" on a 16x20 sheet of Bergger Cot 320 rag cotton paper. The image is formed from an equal volume of gold chloride and iridium chloride, hence the name "Auridiotype Supreme" for the process. The print is identified as "1/1 Auridiotype (Au/Ir). Skull" in pencil and signed by the photographer in pencil.
Until World War One iridium was quite widely used for printing photographs. Iridium was added in varying proportions to platinum or palladium for the purpose of enriching blacks. Early in the 20th century, a Viennese gentleman named Moll announced the availability of a "chloride of iridium printing out paper". I have found one review of the product in the British Journal of Photography. The results of printing out iridium are comparable to platinum but with a somewhat coarser appearance (and richer blacks). Not until my Chrysotype Supreme process (formerly named the Texas Chrysotype), which yields grainless, continuous tone gold prints that rival platinum and palladium, was it possible to mix iridium and gold to form an image. The characteristics, at proportions of half iridium and half gold, are invisible grain, smooth tonal gradation with a wide range, and an almost scientifically precise rendering.
The formula for the process is identical to the Chrysotype Supreme with the substitution of up to three quarters of the gold chloride with an equal number of drops of 10% iridium chloride.