The “Mercury” Stereoscope is a Holmes system stereoscopic viewer for stereoscopic photographs, with a single 7 x 7 cm image, produced in 1900–1920 by Underwood & Underwood from New York (USA). One of the simplest designs of stereoscopic viewers was the “open” viewer system, invented by Oliver Wendell Holmes in 1861. This was an extremely simple design, equipped with an eyepiece with lenses, including an appropriately curved wooden or metal sun visor. The Underwood & Underwood Company sold millions of stereoscopic photos, thanks to this very cheap production model of the viewer.
James Hammond obtained a patent for the construction of the machine in 1881, and its serial production began in 1884. The presented model 12 was created in the early 20th century in two versions; one was characterized by an arched two-row keyboard, typical of the early Hammonds; and the second, with a three-row keyboard, was typical for three-register machines. The final version, seen in the presented object, was introduced at the end of the nineteenth century along with the growing competition of lever-typing machines, with a typical arrangement of keys in straight rows.
The Marconi radio set is a high quality luxury battery-operated radio set produced by Polskie Zakłady Marconi S.A. This Warsaw branch of the Marconi Wireless Telegraph Company Ltd. London, the company established by the undisputed inventor of radiophony, Guglielmo Marconi, was established in 1928.