It is a large x-ray tube of the Coolidge type having a length of 100 cm mounted on a wide wooden platform by means of two porcelain insulators 40 cm in length.
Coolidge tubes differ from focus tubes in that their vacuums are far greater, the electronic beam is produced by thermoionic effect and the anode acts as the anticathode; they deliver far more intense beams of x-rays and, being more regular and constant, they replaced focus tubes in the long run.
In the tube presented here, the cathode is a small, flat spiral protected by a thin, cylindrical sheath and the anticathode is a thick, square plate (about 3 x 3 cm) at an angle of 45 degrees, held by a long cylindrical tube of metal having very thin walls, which favours cooling.
A testing label dated 16 June 1929 indicates that the maximum working tension is 160 kilovolts, the discharge current is 4 milliamperes and the maximum supply current is 4.2 amperes.