This tintype is one that is in very poor condition - a toss up among this, #28 & #40 of all of the photographs in the Johnston Family Album. It has been a very difficult restoration job - very, very time consuming, and it's nowhere close to being finished. Fortunately, as I rescued the images it became apparent who the boys were - my great grandfather James and his younger brother Arthur.
Dating? The well-defined side part in the hair with the hair just slightly over the ears, scarf-type tie, 3-button jackets missmatched with the pants and loose-fitting sleeves indicate somewhere around 1875-80. Fortunately their brother William and sister Mary had a photograph taken which was put in the same type of holder and dated 1878. The only difference is the backgrounds which may indicate that this photo was done slightly later, even if only time enough for the new background to have arrived and be hung.