In 1887 he concluded his studies with a PhD. Since 1884, Koechlin had been a voluntary collaborator of the Imperial Mineralogical-Petrographical
Department of the Natural History Museum. He not only drew up the plans for the new installation of the mineralogical collections
in the new premises on the Ring, he also conducted the necessary classification work. He declined to undertake larger scientific
investigations in favour of establishing a minutely detailed inventory of the fast-growing collections at that time. His listings
of the diverse pieces which constituted the various collections, used only for internal purposes at the time, are still considered
indispensable today when undertaking practical work in connection with the objects.
In spite of his assiduity, Koechlin was only appointed first curator in 1912. In 1920, he became Director of the Mineralogical-Petrographical
Department and in 1922 he retired as privy councillor. He died in Vienna on 11 February 1939.