This series of microscopes was introduced about 1875 by Leitz. In 1890 they changed to standard RMS threaded objectives (see G27). This microscope includes the 1/12 inch homogeneous oil immersion lens and the special condenser for it. These were first introduced in 1882. This became one of the bestselling objective lenses with over 33000 of the RMS version sold between 1890 and 1905.