Yes is a military special valve-tester (tube) for the transmitting tube type RL12P35 (The RL12P35 is a 35 Watt transmitting pentode. It was designed for short wave communications in the 50 meter to 4.5 meter band).
The tester box is being opened and a RL12P35 is placed in its socket. When the box is then closed, the valve connections at the top of the valve connect itself automatically.
With this tester could prove the short-circuit between filament and cathode, measuring the anode current or static amplification of the RL12P35 valve.