Glass plates / photo negatives
Photographic glass plates (negatives) preceded photographic film as a capture medium in photography. The light-sensitive emulsion of silver salts was coated on a glass plate, typically thinner than common window glass, instead of a clear plastic film. This form of photographic material largely faded from the consumer market in the early years of the 20th century, as more convenient and less fragile films were increasingly adopted.
The same Ashkari soldier is also possibly found in a newspaper photo of 1905 guarding chained prisoners in Kilwa (see slide-show)