These two ladies had their photo done in Edinburgh Scotland at the Parisian Photo Co. I found possible dates for this studio (1887-93) here at this site.
The dresses do not appear to have bustles of the late bustle period (1883-89)…
but do have larger sleeves of the Belle Epoche so I think this would be in the 90’s range for this photo. If this studio lasted until ’93 then this photo is ’90-93.