His age in this photograph is estimated to be about age 28-35, which would lead to a 1876-1883 timeframe. In this timeframe, William had just returned from his tour with the NWMP and began his life and family in Montreal. Given that he was married on January 25, 1877, it is suggested that this is his wedding or engagement portrait. The original portrait is on ferro-tin and could be a mate to the ferro-tin Elizabeth Black's wedding portrait.
The Leonhardt family lent the original of this ferro-tin Studio Portrait to Dave Jordan in 1990 who photographed it. The Leonhardt connection to the Jordans is Margaret Jane Jordan and Muriel Leonhardt were Knowles sisters.
If you would like to add information about this picture, please contact Dave Jordan, a 2x g-grandson of William and Isabella Knowles. The Picture Reference Number is Digitized Negative: 161-06.