Visor stereoscopic RADA-STANDARD I (System Derpsch) metal guide dispersion, lacquered matt black special slide frames Rada metal 45 x 101 mm (as shown) or slide frame format 41 x 101 mm (Realist, - Belplasca, - RBT format). Adjustable for any visual acuity. Available with lenses or pressed glass lens f 38 f 48 and terrestrial optical f 58 mm. It made around 1955 by RADA-Metallwarenfabrik, Frankfurt / M.- Rodelheim. Other models: RADA-STANDARD III lighting. Measures Viewer / Glass 4,5x10,5