The two Chinese seem to wear a pigtail, as it was the custom during the Qing era. This suggests that the photo was taken before 1912. Note the presence of a sikh policeman, also frequently featured on early photos.
Institut d'Asie Orientale
ENS de Lyon, Site Descartes
15 Parvis René Descartes
69341 Lyon Cedex 07 France
Labo Junior Nhumérisme
Séminaire EHESS "L'historien et l'espace"
Séminaire EHESS "Images et histoire"