The Midland Leather Works mentioned by Rob at 55-56 Macdonald St is the works which Tinpot was interested in. Charles Mason, whip thong manufacturer appears in the directories at this address in 1872 and continues the business until the 1920s, when , presumably the nees for horsewhips was waning.
That said Tinpot states he is interested in a family at 86 Macdonald st. this is in fact nearer , almost next door in fact to the other leather business in the street. This firm, marked as the Phoenix leather works on the c1889 map at the west end of Macdonald st is listed in the 1884 Kellys as William Baggot, leather dresser, and in the 1880 Kellys as Gates & Baggott, leather dressers. In Whites directory of 1873 (which would have referred to the time or just after the 1871 census) it is occupied by G Ritchie, tanner & leather dresser. The first occupant of the site seems to be Edwin Harford, recorded in the 1855 directory as morocco leather dresser & asses' skin manufacturer, 90 Macdonald St. He is there till at least 1858, but by 1862 the factory is occupied by Frederick Ritchie (Chamois etc leather dressers)., in 1867 described as morocco leather dressers, In 1867 a partnership with William Warrilow was dissolved. By 1873 the firm has become G Ritchie, leather dresser,but in 1876 another partnership with A Gates is dissolved, and , as a result in he 1879 directory, which would probably refer to 1877, the entry for the firm is Gates & Baggott