Waveline 709 (WR-62) 12.4-18 GHz, 0-60 dB, 2 W, Rotary Vane Attenuator
Exact item shown, WR42 vane type attenuator, rotating the wheel raises and lowers the vane adjusting the attenuation, when you have it where you want it, tightening the lock screw locks it into position.