This large barrel or drum compound microscope was designed according to some by Benjamin Martin. Others assign it to Braunhofer and still others to Oberhauser who was the one who perfected it. This device is the largest of those manufactured as it is 27 cm high. An unusual size. It includes a series of advances over the basic model: it incorporates an internal rack on which the focus wheel acts, a larger mirror and a larger diameter plate. The model is included in Billing’s Catalog fig.50 page 27 and fig. 361 on page 389.