Embossed wax capsule, secure on top but broken to side, reads John Somerville & Co, Leith.
 
John Somerville & Co, Leith became major shareholders of Glendronach distillery after the death of previous owner Walter Scott in 1887. After which continued to age their whisky in old sherry barrels. In 1897 John Somerville & Co merged with Blyth & Cameron, Brewers in Edinburgh to form the North British Brewery. It follows then, that this bottle of whisky was distilled and bottled prior to that date. Somewhere between 1887 and 1897. 
(information: University of Glasgow Archive Services & scotchwhisky.com)