Russian double tetrode GU-18 (ГУ-18) in original metal box. Comparing to the GU-18-1 is version GU-18 recently becoming really rare. There are 2 bigger and one smaller sections for storage inside the box which may be used for smaller components. Outside dimensions of the box: 12,3 x 12,3 x 6,3 cm. Original datasheet of GU-18 is included. There are some small oxidation marks after closer inspection. Please see the full gallery. Unused, longer time stored items. Year of production: 1970.