Subject: Three sergeants. I've enlarged the distinctive items of their uniforms, and welcome any additional information about what they signify.
Photographer: Wing Chong
Format: cabinet card
Date: c.1885. The back of the card gives the photographer's address as "No. 74, Queen's Road, Upstairs. Opposite the Central Market." Wing Chong was there in 1885 (see https://gwulo.com/node/31857)
Photo courtesy of The Pottinger Hong Kong hotel.