What a lovely photographic study. I would agree with the date line given. The woman on the left of the photograph has her bonnet placed to the back of her head (same as the other woman has) which is tied under the chin by broad stringing (ribbons) this was a fashion trend in the late 1850's and throughout the 1860's. Her sleeving may be a style known as a Bishop sleeve but I can not see its full length but as she has a large epaulette at the shoulder seam it would have been taken before 1870 as this was the date period that this form of style started to disappear from fashion. The woman on the right has Gabrielle sleeving which was/is a style formed by the bunching up of the sleeve material in to seperate "puffs" running down the arm. Again this style can be found in the 1860's. The man is seen wearing a three piece Sac suit with the material appearing to be of the same type for all three pieces. Both Jacket (which would have only been fastened by the very top button) and waist coat are edged off and the waist coat is buttoned high and would show above the lapels of the Sac coat.
As for the photographer I can find nothing about him on line save for a reference to a Frederick Downer, a Frederick Downer & Son, and a Frederick Downer junior, all of which relate to being photographers. Wether this is the same man or not I do not know but looking at the 1881 census Frederick Downer, artist and photographer, had a son also called Frederick so the latter may have been the " & son" and "junior" mentioned above.
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