 Complete the following phrase:  Their opus 1 was exhibited at the Vienna World Exhibition in Vienna, at which it won a gold medal; this organ is now in the church of St Peter  Paul in Jaktař. One of their first changes from their fathers work was the replacement of slider chests with mechanical cone chests. Their first year saw the production of three organs. Their reputation grew apace: in 1874 they won their first commission in the Imperial Capital, Vienna, followed in 1875 by a commission in Hungary. Their first commission in a non-Habsburg country was in 1876 in Norway. They exhibited two salon organs at the 1878 