G-MKDA 747-200 Pitot-Static Leak Tester

This is a Pitot-Static Leak Tester or a Pressure Transducer/Air Data Sensor (likely a vintage model).
It is designed to connect to the aircraft's pneumatic lines—the systems that measure airspeed, altitude, and vertical speed. Based on the "P" and "S" markings near the ports, it is specifically designed to interface with the Pitot and Static systems.
Breakdown of the Ports:
• The Red Port (P): This is the Pitot connection. In flight, this measures "impact" air pressure to determine airspeed. The red color is a standard aviation coding for pitot lines (often associated with "hot" or high-pressure lines).
• The Yellow/Gold Port (S): This is the Static connection. This measures the ambient atmospheric pressure to determine altitude.
• The Electrical Connector (Top): This is a multi-pin "Mil-Spec" (Military Specification) circular connector. This sends the pneumatic data as electrical signals to the cockpit instruments or a flight data computer.
What does it do?
Given its cylindrical, sealed shape and the mounting flange, this is likely a Remote Air Data Sensor.
Instead of running air hoses all the way to the back of the instruments in the dashboard (which can leak or lag), this unit stays close to the external probes, converts the air pressure into electrical signals, and "talks" to the cockpit electronically.